Branched vessel endoluminal device

ABSTRACT

An endoluminal prosthesis comprises a prosthetic trunk having a trunk lumen and a trunk wall, a first prosthetic branch having a first branch lumen and a branch wall, and a second prosthetic branch having a second branch lumen. The first branch lumen and the second branch lumen are both in fluid communication with the trunk lumen through the trunk wall and the second branch lumen is in fluid communication with the first branch lumen through the branch wall. Additional devices, systems, and methods are disclosed.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/174,451, dated Jul. 16, 2008, which is a continuation-in-part of U.S.patent application Ser. No. 11/403,605, filed Apr. 13, 2006 (now U.S.Pat. No. 7,407,509), which claims the benefit of the filing date under35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No.60/671,410, filed Apr. 13, 2005, which is a continuation-in-part of U.S.patent application Ser. No. 10/756,803, filed Jan. 13, 2004 (U.S. Pat.No. 7,105,020), which claims the benefit of the filing date under 35U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No.60/439,923, filed Jan. 14, 2003; U.S. Provisional Patent ApplicationSer. No. 60/478,107, filed Jun. 11, 2003; and U.S. Provisional PatentApplication Ser. No. 60/510,636, filed Oct. 10, 2003, all of which areincorporated herein by reference.

TECHNICAL FIELD

This invention relates to prostheses for implantation within the humanor animal body for the repair of damaged vessels, ducts or otherphysiological passageways.

BACKGROUND

Throughout this specification, when discussing the application of thisinvention to the aorta or other blood vessels, the term “distal” withrespect to a prosthesis is intended to refer to a location that is, or aportion of the prosthesis that when implanted is, further downstreamwith respect to blood flow; the term “distally” means in the directionof blood flow or further downstream. The term “proximal” is intended torefer to a location that is, or a portion of the prosthesis that whenimplanted is, further upstream with respect to blood flow; the term“proximally” means in the direction opposite to the direction of bloodflow or further upstream.

The functional vessels of human and animal bodies, such as blood vesselsand ducts, occasionally weaken or even rupture. For example, the aorticwall can weaken, resulting in an aneurysm. Upon further exposure tohemodynamic forces, such an aneurysm can rupture. One study found thatin Western European and Australian men who are between 60 and 75 yearsof age, aortic aneurysms greater than 29 mm in diameter are found in6.9% of the population, and those greater than 40 mm are present in 1.8%of the population.

One surgical intervention for weakened, aneurysmal or ruptured vesselsinvolves the use of an endoluminal prosthesis to provide some or all ofthe functionality of the original, healthy vessel and/or preserve anyremaining vascular integrity by replacing a length of the existingvessel wall that spans the site of vessel failure.

It is preferable that these prostheses seal off the failed portion ofthe vessel. For weakened or aneurysmal vessels, even a small leak in theprosthesis may lead to the pressurization of or flow in the treatedvessel, which aggravates the condition the prosthesis was intended totreat. A prosthesis of this type can, for example, treat aneurysms ofthe abdominal aortic, iliac, or branch vessels such as the renalarteries.

An endoluminal prosthesis can be of a unitary construction, or becomprised of multiple prosthetic modules. A modular prosthesis allows asurgeon to accommodate a wide variation in vessel morphology whilereducing the necessary inventory of differently sized prostheses. Forexample, aortas vary in length, diameter and angulation between therenal artery region and the region of the aortic bifurcation. Prostheticmodules that fit each of these variables can be assembled to form aprosthesis, obviating the need for a custom prosthesis or largeinventories of prostheses that accommodate all possible combinations ofthese variables. A modular system may also accommodate deployment byallowing the proper placement of one module before the deployment of anadjoining module.

Modular systems are typically assembled in situ by overlapping thetubular ends of the prosthetic modules so that the end of one modulesits partially inside the other module, preferably formingcircumferential apposition through the overlap region. This attachmentprocess is called “tromboning.” The connections between prostheticmodules are typically maintained by the friction forces at the overlapregion and enhanced by the radial force exerted by the internalprosthetic module on the external prosthetic modules where the twooverlap. The fit may be further enhanced by stents fixed to the modulesat the overlap region.

A length of a vessel which may be treated by these prostheses may haveone or more branch vessels, i.e. vessels anastomosed to the main vessel.The celiac, superior mesenteric, left common carotid and renal arteries,for example, are branch vessels of the aorta; the hypogastric artery isa branch vessel of the common iliac artery. If these branch vessels areblocked by the prosthesis, the original blood circulation is impeded,and the patient can suffer. If, for example, the celiac artery isblocked by the prosthesis, the patient can experience abdominal pain,weight loss, nausea, bloating and loose stools associated withmesenteric ischemia. The blockage of any branch vessel is usuallyassociated with unpleasant or even life-threatening symptoms.

When treating a vessel with an endoluminal prosthesis, it is thereforepreferable to preserve the original circulation by providing aprosthetic branch that extends from the main prosthetic module to abranch vessel so that the blood flow into the branch vessel is notimpeded. For example, the aortic section of the Zenith® abdominal aorticprosthesis (Cook Incorporated, Bloomington, Ind.), described below, canbe designed to extend above the renal arteries and to have prostheticbranches that extend into and provide flow to the renal arteries.Alternatively, the iliac branches of a bifurcated aortic prosthesis canbe designed to extend into and provide flow to the correspondinghypogastric arteries. Branch extension prosthetic modules (“branchextensions”) can form a tromboning connection to the prosthetic branchto extend further into the branch artery. Furthermore, some aneurysmsextend into the branch vessels. Deploying prosthetic branches and branchextensions into these vessels may help prevent expansion and/or ruptureof these aneurysms. High morbidity and mortality rates are associatedwith these aneurysms.

Typically, existing prosthetic branches have a straight y- or t-shapedconnection to the main endoluminal graft. Examples of such prostheticbranches and their associated branch extensions are shown in U.S. Pat.Nos. 6,520,988 and 6,579,309. Some of these branch extensions and theirassociated prosthetic branches may dislocate, kink and/or cause poorhemodynamics. These problems may lead to thrombogenesis and endoleaks atthe interconnection of the prosthetic branch and branch extension.

BRIEF SUMMARY

In one aspect, an endoluminal prosthesis may be provided and comprise aprosthetic trunk and first and second prosthetic branches. Theprosthetic trunk comprises a trunk lumen extending therethrough and atrunk wall. The first prosthetic branch extends from the trunk wall andcomprises a first branch lumen extending therethrough and a branch wall.The second prosthetic branch extends from the branch wall and comprisesa second branch lumen. The first and second branch lumens are both influid communication with the trunk lumen through the trunk wall and thesecond branch lumen is in fluid communication with the first branchlumen through the branch wall.

At least one, and in some examples both, of the first and secondprosthetic branches may be disposed longitudinally along andcircumferentially about the prosthetic trunk. In some examples, one ofthe prosthetic branches may be disposed longitudinally along andcircumferentially about the other of the prosthetic branches. Theprosthetic branches may have any suitable shape. For example, at leastone of the branches may be tapered.

In another aspect, an endoluminal prosthesis may be provided andcomprise a prosthetic trunk and a stent attached to the prosthetictrunk. The prosthetic trunk comprises a trunk lumen extendingtherethrough, a wall, and an anastomosis in the wall. The stent has agenerally tubular stent body that provides radial support to theprosthetic trunk. The stent body alternates endlessly about alongitudinal axis of the prosthetic trunk between a first stent patternand a second stent pattern. The first stent pattern comprises a loophaving a contour that contacts and supports the entire perimeter of theanastomosis. In some examples, the second stent pattern has a generallyzigzag shape. The loop may have any contour that matches the contour ofthe anastomosis. In some examples, the loop has an ovoid shape.

In another aspect, an endoluminal prosthesis may be provided andcomprise a prosthetic trunk having a trunk lumen, a prosthetic branchhaving a branch lumen, and a stent. The stent has a stent pattern thatalternates endlessly about the perimeter of the stent between a firsttubular stent region disposed about a first axis and a second tubularstent region disposed about a second axis. The first stent region isattached to and supports at least a portion of the prosthetic trunk andthe second stent region is attached to and supports at least a portionof the prosthetic branch.

In some examples, the endless alternating stent pattern includes agenerally zigzag shape. The first and second stent regions may havediameters that are generally the same, or they may have differentdiameters. The first stent axis and the second stent axis are arrangedaccording to the arrangement of the prosthetic trunk and the prostheticbranch. For example, the first and second stent axes may be generallycollinear. In some examples, the stent may have a figure-8 shape.

In some examples, the prosthetic branch may be disposed, at least inpart, inside the prosthetic trunk lumen. Likewise, the prosthetic branchmay be disposed, at least in part, outside the prosthetic trunk lumen.The stent may be disposed on the interior and/or exterior surface of theprosthetic trunk and the prosthetic branch. For example, at least aportion of the first stent region may be disposed on an interior surfaceof the prosthetic trunk. In these examples, at least a portion of thefirst stent region may be disposed on a surface of the prostheticbranch, for example an exterior surface of the prosthetic branch. Insome examples, at least a portion of the second stent region may bedisposed on an exterior surface of the prosthetic branch.

Other aspects of the present invention will become apparent inconnection with the following description of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic anterior view of an endoluminal prosthesis witha y-shaped prosthetic branch;

FIG. 2 shows a schematic anterior view of an endoluminal prosthesis witha helical prosthetic branch;

FIG. 3a shows a side view of an embodiment of an endoluminal prosthesiswith a helical prosthetic branch;

FIG. 3b shows another side view of the embodiment of FIG. 3 a;

FIG. 3c shows an embodiment of an extension module;

FIG. 4a shows a schematic top view of an embodiment of an endoluminalprosthesis;

FIG. 4b shows a schematic front view of the embodiment of FIG. 4 a;

FIG. 4c shows a skeletal schematic front view of the embodiment of FIG.4 a;

FIGS. 5a-d show preferable steps for creating an enlarged anastomosis;

FIG. 6a shows a schematic anterior view of an embodiment of anendoluminal prosthesis;

FIG. 6b shows a skeletal view of the embodiment of FIG. 6 a;

FIG. 7a shows a schematic anterior view of an embodiment of anendoluminal prosthesis;

FIG. 7b shows a top view the embodiment of FIG. 7 a;

FIG. 8a shows an anterior view of an embodiment of an endoluminalprosthesis;

FIG. 8b shows a side view of the embodiment of FIG. 8 a;

FIG. 8c shows another side view of the embodiment of FIG. 8 a;

FIG. 8d shows a posterior view of the embodiment of FIG. 8 a;

FIG. 9a shows a skeletal anterior view of an embodiment of anendoluminal prosthesis;

FIG. 9b shows a schematic anterior view of the embodiment of FIG. 9 a;

FIG. 10a shows a schematic anterior view of an embodiment of anendoluminal prosthesis;

FIG. 10b shows a schematic top view of the embodiment of FIG. 10 a;

FIGS. 11a-c show three views of an embodiment of an endoluminalprosthesis;

FIG. 12a shows a skeletal anterior view of an embodiment of anendoluminal prosthesis;

FIG. 12b shows a schematic anterior view of the embodiment of FIG. 12 a;

FIG. 12c shows a schematic top view of the embodiment of FIG. 12 a;

FIG. 13a shows a schematic anterior view of an embodiment of anendoluminal prosthesis that has crimps;

FIG. 13b shows a skeletal view of the embodiment of FIG. 13 a;

FIG. 13c shows a schematic top view of the embodiment of FIG. 13 a;

FIGS. 14a-b show two views of an embodiment of an endoluminalprosthesis;

FIG. 15a shows a modular prosthesis that has a prosthetic trunk modulein the left iliac artery connected to a prosthetic branch in thehypogastric artery;

FIG. 15b shows the modular prosthesis of 15 a, where the prosthetictrunk and aortic module are connected via an intervening prostheticmodule;

FIG. 15c shows an intervening prosthetic module;

FIG. 16 shows a helical branch having annular stents;

FIG. 17 shows an annular stent sutured to the distal ostium of a helicalbranch;

FIG. 18 shows a helical branch having a helical stent;

FIG. 19 shows the helical stent coiled at the branch ostium;

FIG. 20 shows a stent at the branch anastomosis;

FIGS. 21a-b show two modified Z-stents that may be used to support,without obstructing, the branch-trunk anastomosis;

FIG. 21c shows a modified Z-stent that has a loop for supporting thebranch trunk anastomosis;

FIG. 21d shows a modified Z-stent that has an asymmetrical bend forsupporting the distal aspect of the branch-trunk anastomosis.

FIG. 22a shows the stents of FIGS. 21a-b attached to a graft andpositioned to support a branch-trunk anastomosis;

FIG. 22b shows the stent of FIG. 21c attached to a graft and positionedto support a branch-trunk anastomosis;

FIGS. 23a-d shows different views of a stent designed to maintain theshape of a branch-trunk anastomosis;

FIGS. 23e-f show the stent of FIGS. 23a-d affixed to the inside of abranch adjacent the branch-trunk anastomosis;

FIG. 24a shows a perspective view of a heat-setting fixture for formingthe stent of FIGS. 23a -d;

FIG. 24b shows a plan view of a heat-setting fixture for forming thestent of FIGS. 23a -d;

FIG. 24c shows a perspective view of a part of the heat-setting fixtureused to form the stent of FIGS. 23a -d;

FIG. 24d shows a side view of a heat-setting fixture used to form thestent of FIGS. 23a -d;

FIGS. 25, 26, and 27 a-e show multiple prosthetic branches extendingfrom a prosthetic trunk;

FIGS. 28a-c show an internal helical branch;

FIG. 29 shows a cross-section of a prosthesis having baffles affixed toan internal helical branch;

FIG. 30 shows an internal helical branch within a pocket;

FIG. 31 shows a cross-section of an internal helical branch within apocket;

FIGS. 32a-c show thoracic prosthetic modules having one or more helicalside branches;

FIGS. 33-36 show various perspective views of a prosthesis having abranch and fenestrations;

FIGS. 37 and 38 show skeletal views of the prosthesis of FIGS. 29-32;

FIG. 39 shows a view of the prosthesis in the direction of arrow A ofFIG. 38;

FIG. 40 shows a view of the prosthesis in the direction of arrow B ofFIG. 38;

FIGS. 41a-d show various perspective views of an aortic prosthesishaving a branch and fenestrations;

FIGS. 42a-d show various perspective views of an aortic prosthesishaving a branch and fenestrations;

FIG. 43 shows an apparatus for deploying a bifurcated prosthesis; and

FIG. 44 shows a portion of a device used for deploying a branched vesselprosthesis.

DETAILED DESCRIPTION

Branch vessel prostheses may be formed with prosthetic branches that aredisposed longitudinally and circumferentially with respect to theprosthetic trunk. Such prosthetic branches are termed “helical”prosthetic branches. A branch extension may be connected to the distalend of the helical prosthetic branch by tromboning.

The helical turn in the prosthetic branch may reduce the forces on thebranch extension by shifting the hemodynamic forces from the prostheticbranch and the interconnection between the branch extension to theprosthetic trunk. This may help prevent the branch extension frompulling out under those forces. The helical turn may also allow a widervariation in the radial orientation (“angle of access”) of theprosthetic trunk and may prevent kinking of the prosthetic branch orbranch extension. This design may also improve the hemodynamics by, forexample, promoting laminar flow.

To help understand this description, the following definitions areprovided.

The term “prosthesis” means any replacement for a body part or functionof that body part. It can also mean a device that enhances or addsfunctionality to a physiological system.

The term “endoluminal” describes objects that are found or can be placedinside a lumen in the human or animal body. A lumen can be an existinglumen or a lumen created by surgical intervention. This includes lumenssuch as blood vessels, parts of the gastrointestinal tract, ducts suchas bile ducts, parts of the respiratory system, etc. An “endoluminalprosthesis” is thus a prosthesis that can be placed inside one of theselumens.

The term “stent” means any device or structure that adds rigidity,expansion force or support to a prosthesis. A Z-stent is a stent thathas alternating struts and peaks (i.e., bends) and defines a generallycylindrical lumen. The “amplitude” of a Z-stent is the distance betweentwo bends connected by a single strut. The “period” of a Z-stent is thetotal number of bends in the Z-stent divided by two, or the total numberof struts divided by two.

The term “pull-out force” means the maximum force of resistance topartial or full dislocation provided by a modular prosthesis. Thepull-out force of a prosthesis having two interconnected modules can bemeasured by an MTS Alliance RT/5® tensile testing machine (MTSCorporation, Eden Prairie, Minn.). The MTS machine is connected to acomputer terminal that is used to control the machine, collect, andprocess the data. A pressurization pump system is attached to the loadcell located on the tensile arm of the MTS machine. One end of theprosthesis is connected to the pressurization pump, which provides aninternal pressure of 60 mm Hg to simulate the radial pressure exerted byblood upon the device when deployed in vivo. The other end of theprosthesis is sealed. The prosthesis is completely immersed in a 37° C.water bath during the testing to simulate mean human body temperature.The MTS machine pulls the devices at 0.1 mm increments until the devicesare completely separated. The computer will record, inter alia, thehighest force with which the modules resist separation, i.e. thepull-out force.

The term “endoleak” refers to a leak around or through an endoluminalprosthesis. Endoleaks can occur through the fabric of a prosthesis,through the interconnections of a modular prosthesis, or around the endsof the prosthesis, inter alia. Endoleakage may result in therepressurizing of an aneurysm.

The term “branch vessel” refers to a vessel that branches off from amain vessel. Examples are the celiac and renal arteries which are branchvessels to the aorta (i.e., the main vessel in this context). As anotherexample, the hypogastric artery is a branch vessel to the common iliac,which is a main vessel in this context. Thus, it should be seen that“branch vessel” and “main vessel” are relative terms.

The term “prosthetic trunk” refers to a portion of a prosthesis thatshunts blood through a main vessel. A “trunk lumen” runs through theprosthetic trunk.

The term “prosthetic branch” refers to a portion of a prosthesis that isanastomosed to the prosthetic trunk and shunts blood into and/or througha branch vessel.

A “peripheral prosthetic branch” is a prosthetic branch that isanastomosed to the side of a prosthetic trunk. This is distinguishedfrom a “contralateral prosthetic branch,” which is a prosthetic branchthat results from a “pant leg” bifurcation. The bifurcation may beasymmetrical, i.e. the two “legs” may have different diameters orlengths.

The term “branch extension” refers to a prosthetic module that can bedeployed within a branch vessel and connected to a prosthetic branch.

The term “helical” or “helically” describes a prosthetic branch that isoriented circumferentially about and longitudinally along a prosthetictrunk. “Helical” is not restricted to a regular helix or a full 360°circumferential turn.

“Longitudinally” refers to a direction, position or length substantiallyparallel with a longitudinal axis of a reference, and is the length-wisecomponent of the helical orientation.

“Circumferentially” refers to a direction, position or length thatencircles a longitudinal axis of reference, and is the radial componentof a helical orientation. Circumferential is not restricted to a full360° circumferential turn nor a constant radius.

“Anastomosis” refers to a connection between two lumens, such as theprosthetic trunk and prosthetic branch that puts the two in fluidcommunication with each other. “Anastomosing” refers to the process offorming an anastomosis.

The term “angle of incidence” refers to the angle of intersection of alongitudinal axis of a prosthetic branch and a line on the prosthetictrunk that runs longitudinally through the anastomosis.

The term “skew” refers to the angle of out-of-plane rotation of theprosthetic branch, relative to the longitudinal axis of the prosthetictrunk, as measured at or near the anastomosis.

The term “angle of access” refers to the acceptable range of radialorientation of the branched prosthesis about the longitudinal axis ofthe prosthetic trunk. Through that range, the distal ostium of theprosthetic branch is close enough to the branch vessel so that thebranch extension can be properly deployed into the branch vessel to forma connection with the prosthetic branch.

FIG. 1 shows a schematic representation of a prosthetic branch 12anastomosed to the prosthetic trunk 10 in a y-configuration. A branchextension 14 forms a tromboning connection with the prosthetic branch12. The branch extension 14 is positioned at a 45° angle 16 to theprosthetic trunk 10 to accommodate the anatomy in which the totalprosthesis is designed to sit. The angle 16 of the branch extension 14causes it to bear forces in the y-direction 15, as a result of the bloodpressure and momentum of the blood flow through the prosthetic branch 12and branch extension 14.

The connection between the branch extension 14 and the prosthetic branch12 is maintained by friction forces. Therefore, if the forces in they-direction 15 borne by the branch extension 14 exceed the frictionforces that maintain the connection, the branch extension 14 maydisconnect from the branch 12. This is a dangerous outcome for thepatient, as the disconnection can result in a repressurization of theregion surrounding the prosthetic branch 12 and the prosthetic trunk 10.

FIG. 2 shows a schematic representation of one embodiment of the presentinvention. In this embodiment, the prosthetic branch 22 is anastomosedto the prosthetic trunk 20. A branch extension 25 forms a tromboningconnection with the prosthetic branch 22. The branch extension 25 ispositioned at an about 60-70° angle 24 to the prosthetic trunk 20 toaccommodate the anatomy in which the total prosthesis is designed tosit, although it can be placed at any suitable angle. The prostheticbranch 22 turns about the prosthetic trunk 20 to form a partial helix.

The angle 24 of the prosthetic branch 22 creates flow forces in they-direction 23 as a result of the momentum of the blood flow through andphysiological blood pressure in the branch 22, just as in the prosthesisof FIG. 1. However, unlike in FIG. 1, the prosthetic branch 22 bearsmuch of these y-forces and is supported by its attachment 27 to theprosthetic trunk 20. Thus, the attachment 27 bears at least some of they-direction forces instead of the load being placed on theinterconnection 21 and the prosthetic branch 22. This helps prevent acommon failure mode known in branched prostheses. A prosthetic extensionmodule 25 may form a tromboning interconnection with the prostheticbranch 22.

FIG. 3a shows another embodiment of the present invention. Thisembodiment is suitable for deployment into the left iliac artery andbranching into the left hypogastric artery, although it can be adaptedfor other vessels. An embodiment suitable for deployment into the rightiliac artery could be a longitudinal mirror-image of the prosthesis 40of FIG. 3a . The prosthesis 40 includes a prosthetic trunk 42 and aperipheral prosthetic branch 44. For this prosthesis 40, and the othersdiscussed herein, the prosthetic branch 44 preferably curves around theanterior of the prosthetic trunk 42 as shown, although, as analternative it may curve around the posterior of the prosthetic trunk42. The prosthetic branch 44 is in fluid communication with theprosthetic trunk 42 through the anastomosis 46. The anastomosis 46 ispreferably infundibular, i.e. funnel-shaped, as shown. This mimics atypical physiological anastomosis, and improves the hemodynamics of flowinto the prosthetic branch 44. The prosthetic branch 44 is preferablysutured to the prosthetic trunk 42 to form a blood-tight seal. Theproximal end of the prosthetic trunk may have a scallop cut into it inorder to facilitate deployment of the prosthesis 40, described below.

The prosthetic trunk 42 is preferably made of woven polyester having atwill weave and a porosity of about 350 ml/min/cm² (available fromVascutek® Ltd., Renfrewshire, Scotland, UK). The prosthetic branch 44 ispreferably made of seamless woven polyester. The prosthetic trunk 42 andprosthetic branch 44 can also be made of any other at leastsubstantially biocompatible material including such fabrics as otherpolyester fabrics, polytetrafluoroethylene (PTFE), expanded PTFE, andother synthetic materials known to those of skill in the art. Naturallyoccurring biomaterials, such as collagen, are also highly desirable,particularly a derived collagen material known as extracellular matrix(ECM), such as small intestinal submucosa (SIS). Other examples of ECMsare pericardium, stomach submucosa, liver basement membrane, urinarybladder submucosa, tissue mucosa, and dura mater. SIS is particularlyuseful, and can be made in the fashion described in U.S. Pat. No.4,902,508 to Badylak et al.; U.S. Pat. No. 5,733,337 to Carr; U.S. Pat.No. 6,206,931 to Cook et al.; U.S. Pat. No. 6,358,284 to Fearnot et al.;17 Nature Biotechnology 1083 (November 1999); and WIPO Publication WO98/22158 of May 28, 1998, to Cook et al., which is the publishedapplication of PCT/US97/14855. All of these references are incorporatedherein by reference. It is also preferable that the material isnon-porous so that it does not leak or sweat under physiologic forces.

Graft materials may also include porous polymer sheet of a biocompatiblematerial. Examples of biocompatible polymers from which porous sheetscan be formed include polyesters, such as poly(ethylene terephthalate),polylactide, polyglycolide and copolymers thereof; fluorinated polymers,such as polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE) andpoly(vinylidene fluoride); polysiloxanes, including polydimethylsiloxane; and polyurethanes, including polyetherurethanes, polyurethaneureas, polyetherurethane ureas, polyurethanes containing carbonatelinkages and polyurethanes containing siloxane segments. In addition,materials that are not inherently biocompatible may be subjected tosurface modifications in order to render the materials biocompatible.Examples of surface modifications include graft polymerization ofbiocompatible polymers from the material surface, coating of the surfacewith a crosslinked biocompatible polymer, chemical modification withbiocompatible functional groups, and immobilization of a compatibilizingagent such as heparin or other substances. Thus, any polymer that may beformed into a porous sheet can be used to make a graft material,provided the final porous material is biocompatible. Polymers that canbe formed into a porous sheet include polyolefins, polyacrylonitrile,nylons, polyaramids and polysulfones, in addition to polyesters,fluorinated polymers, polysiloxanes and polyurethanes as listed above.Preferably the porous sheet is made of one or more polymers that do notrequire treatment or modification to be biocompatible. More preferably,the porous sheet includes a biocompatible polyurethane. Examples ofbiocompatible polyurethanes include Thoralon® (Thoratec, Pleasanton,Calif.), Biospan®, Bionate®, Elasthane®, Pursil® And Carbosil® (PolymerTechnology Group, Berkeley, Calif.).

Preferably the porous polymeric sheet contains the polyurethaneThoralon®. As described in U.S. Patent Application Publication No.2002/0065552 A1, incorporated herein by reference, Thoralon® is apolyetherurethane urea blended with a siloxane-containing surfacemodifying additive. Specifically, the polymer is a mixture of basepolymer BPS-215 and an additive SMA-300. The concentration of additivemay be in the range of 0.5% to 5% by weight of the base polymer. TheBPS-215 component (Thoratec) is a segmented polyether urethane ureacontaining a soft segment and a hard segment. The soft segment is madeof polytetramethylene oxide (PTMO), and the hard segment is made fromthe reaction of 4,4′-diphenylmethane diisocyanate (MDI) and ethylenediamine (ED). The SMA-300 component (Thoratec) is a polyurethanecomprising polydimethylsiloxane as a soft segment and the reactionproduct of MDI and 1,4-butanediol as a hard segment. A process forsynthesizing SMA-300 is described, for example, in U.S. Pat. Nos.4,861,830 and 4,675,361, which are incorporated herein by reference. Aporous polymeric sheet can be formed from these two components bydissolving the base polymer and additive in a solvent such asdimethylacetamide (DMAC) and solidifying the mixture by solvent castingor by coagulation in a liquid that is a non-solvent for the base polymerand additive.

Thoralon® has been used in certain vascular applications and ischaracterized by thromboresistance, high tensile strength, low waterabsorption, low critical surface tension, and good flex life. Thoralon®is believed to be biostable and to be useful in vivo in long term bloodcontacting applications requiring biostability and leak resistance.Because of its flexibility, Thoralon® is useful in larger vessels, suchas the abdominal aorta, where elasticity and compliance is beneficial.

In addition to Thoralon®, other polyurethane ureas may be used as aporous sheet. For example, the BPS-215 component with a MDI/PTMO moleratio ranging from about 1.0 to about 2.5 may be used. Such polyurethaneureas preferably include a soft segment and include a hard segmentformed from a diisocyanate and diamine. For example, polyurethane ureaswith soft segments such as polyethylene oxide, polypropylene oxide,polycarbonate, polyolefin, polysiloxane polydimethylsiloxane), and otherpolyether soft segments made from higher homologous series of diols maybe used. Mixtures of any of the soft segments may also be used. The softsegments also may have either alcohol end groups or amine end groups.The molecular weight of the soft segments may vary from about 500 toabout 5,000 g/mole.

The diisocyanate used as a component of the hard segment may berepresented by the formula OCN—R—NCO, where —R— may be aliphatic,aromatic, cycloaliphatic or a mixture of aliphatic and aromaticmoieties. Examples of diisocyanates include tetramethylene diisocyanate,hexamethylene diisocyanate, trimethyhexamethylene diisocyanate,tetramethylxylylene diisocyanate, 4,4′-decyclohexylmethane diisocyanate,dimer acid diisocyanate, isophorone diisocyanate, metaxylenediisocyanate, diethylbenzene diisocyanate, decamethylene 1,10diisocyanate, cyclohexylene 1,2-diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, xylene diisocyanate, m-phenylene diisocyanate,hexahydrotolylene diisocyanate (and isomers),naphthylene-1,5-diisocyanate, 1-methoxyphenyl 2,4-diisocyanate,4,4′-biphenylene diisocyanate, 3,3-dimethoxy-4,4′-biphenyl diisocyanateand mixtures thereof.

The diamine used as a component of the hard segment includes aliphaticamines, aromatic amines and amines containing both aliphatic andaromatic moieties. For example, diamines include ethylene diamine,propane diamines, butanediamines, hexanediamines, pentane diamines,heptane diamines, octane diamines, m-xylylene diamine, 1,4-cyclohexanediamine, 2-methypentamethylene diamine, 4,4′-methylene dianiline, andmixtures thereof. The amines may also contain oxygen and/or halogenatoms in their structures.

In addition to polyurethane ureas, other polyurethanes, preferably thosehaving a chain extended with diols, may be used as a porous sheet.Polyurethanes modified with cationic, anionic and aliphatic side chainsmay also be used. See, for example, U.S. Pat. No. 5,017,664.Polyurethanes may need to be dissolved in solvents such as dimethylformamide, tetrahydrofuran, dimethyacetamide, dimethyl sulfoxide, ormixtures thereof.

The soft segments of these polyurethanes may contain any of the softsegments mentioned above, such as polytetramethylene oxide, polyethyleneoxide, polypropylene oxide, polycarbonate, polyolefin, polysiloxane(i.e., polydimethylsiloxane), other polyether soft segments made fromhigher homologous series of diols, and mixtures of these soft segments.The soft segments may have amine end groups or alcohol end groups.

The hard segment may be formed from any of the diisocyanates listedabove, such as 4,4′-diphenylmethane diisocyanate, tetramethylenediisocyanate, hexamethylene diisocyanate, trimethyhexamethylenediisocyanate, tetramethylxylylene diisocyanate, 4,4′-decyclohexylmethanediisocyanate, dimer acid diisocyanate, isophorone diisocyanate,metaxylene diisocyanate, diethylbenzene diisocyanate, decamethylene 1,10diisocyanate, cyclohexylene 1,2-diisocyanate, 2,4-toluene diisocyanate,2,6-toluene diisocyanate, xylene diisocyanate, m-phenylene diisocyanate,hexahydrotolylene diisocyanate (and isomers),naphthylene-1,5-diisocyanate, 1-methoxyphenyl 2,4-diisocyanate,4,4′-biphenylene diisocyanate, 3,3-dimethoxy-4,4′-biphenyl diisocyanateand mixtures thereof.

The hard segment may be formed from one or more polyols. Polyols may bealiphatic, aromatic, cycloaliphatic or may contain a mixture ofaliphatic and aromatic moieties. For example, the polyol may be ethyleneglycol, diethylene glycol, triethylene glycol, 1,4-butanediol, neopentylalcohol, 1,6-hexanediol, 1,8-octanediol, propylene glycols, 2,3-butyleneglycol, dipropylene glycol, dibutylene glycol, glycerol, or mixturesthereof.

In addition, the polyurethanes may also be end-capped with surfaceactive end groups, such as, for example, polydimethylsiloxane,fluoropolymers, polyolefin, polyethylene oxide, or other suitablegroups. See, for example the surface active end groups disclosed in U.S.Pat. No. 5,589,563, which is incorporated herein by reference.

The porous polymeric sheet may contain a polyurethane having siloxanesegments, also referred to as a siloxane-polyurethane. Examples ofpolyurethanes containing siloxane segments include polyethersiloxane-polyurethanes, polycarbonate siloxane-polyurethanes, andsiloxane-polyurethane ureas. Specifically, examples ofsiloxane-polyurethane include polymers such as Elast-Eon 2® andElast-Eon 3® (Aortech Biomaterials, Victoria, Australia);polytetramethyleneoxide (PTMO) and polydimethylsiloxane (PDMS)polyether-based aromatic siloxane-polyurethanes such as Pursil®-10, -20,and -40 TSPU; PTMO and PDMS polyether-based aliphaticsiloxane-polyurethanes such as Pursil AL-5® and AL-10 TSPU®; aliphatic,hydroxy-terminated polycarbonate and PDMS polycarbonate-basedsiloxane-polyurethanes such as Carbosil®-10, -20, and -40 TSPU (allavailable from Polymer Technology Group). The Pursil®, Pursil-AL®, andCarbosil® polymers are thermoplastic elastomer urethane copolymerscontaining siloxane in the soft segment, and the percent siloxane in thecopolymer is referred to in the grade name. For example, Pursil-10®contains 10% siloxane. These polymers are synthesized through amulti-step bulk synthesis in which PDMS is incorporated into the polymersoft segment with PTMO (Pursil®) or an aliphatic hydroxy-terminatedpolycarbonate (Carbosil®). The hard segment consists of the reactionproduct of an aromatic diisocyanate, MDI, with a low molecular weightglycol chain extender. In the case of Pursil-AL® the hard segment issynthesized from an aliphatic diisocyanate. The polymer chains are thenterminated with a siloxane or other surface modifying end group.Siloxane-polyurethanes typically have a relatively low glass transitiontemperature, which provides for polymeric materials having increasedflexibility relative to many conventional materials. In addition, thesiloxane-polyurethane can exhibit high hydrolytic and oxidativestability, including improved resistance to environmental stresscracking. Examples of siloxane-polyurethanes are disclosed in U.S.Patent Application Publication No. 2002/0187288 A1, which isincorporated herein by reference.

The porous polymer sheet may contain polytetrafluoroethylene or expandedpolytetrafluoroethylene (ePTFE). Films or sheets of ePTFE are typicallyporous without the need for further processing. The structure of ePTFEcan be characterized as containing nodes connected by fibrils. PorousePTFE can be formed, for example, by blending PTFE with an organiclubricant and compressing it under relatively low pressure. Using a ramtype extruder, the compressed polymer is then extruded through a die,and the lubricant is removed from the extruded polymer by drying orother extraction method. The dried material is then rapidly stretchedand/or expanded at elevated temperatures. This process can provide forePTFE having a microstructure characterized by elongated nodesinterconnected by fibrils. Typically, the nodes are oriented with theirelongated axis perpendicular to the direction of stretch. Afterstretching, the porous polymer is sintered by heating it to atemperature above its crystalline melting point while maintaining thematerial in its stretched condition. This can be considered as anamorphous locking process for permanently setting the microstructure inits expanded or stretched configuration. The structure and porosity ofePTFE is disclosed, for example, in U.S. Pat. Nos. 6,547,815 B2;5,980,799; and 3,953,566; all of which are incorporated herein byreference. Structures of porous hollow fibers can be formed from PTFE,and these porous hollow fibers can be assembled to provide a cohesiveporous sheet. Porous hollow fibers containing PTFE are disclosed, forexample, in U.S. Pat. No. 5,024,671, which is incorporated herein byreference.

Polymers can be processed to be porous sheets using standard processingmethods, including solvent-based processes such as casting, spraying anddipping, and melt extrusion processes. Extractable pore forming agentscan be used during processing to produce porous sheets. Examples ofextractable pore forming agents include inorganic salts such aspotassium chloride (KCl) and sodium chloride (NaCl), organic salts, andpolymers such as poly(ethylene glycol) (PEG) and polyvinylpyrrolidone(PVP). Pore forming agents may have a particle size from about 10 μm toabout 500 μm, from about 20 μm to about 100 μm, and from about 10 μm toabout 40 μm. The amount of pore forming agent relative to the polymermay be from about 20 percent by weight (wt %) to about 90 wt %, and fromabout 40 wt % to about 70 wt %. These sizes and amounts of pore formingagents can provide for a high degree of porosity following extraction ofthe pore forming agent. The porosity can be from about 20 wt % to about90 wt %, and from about 40 wt % to about 70 wt % of the final product.

Porous sheets may be in the form of a microporous, open-celled structurein which the pores are substantially interconnected. Microporousstructures can be formed by extrusion of a mixture of polymer and one ormore blowing agents. Microcellular polymeric foams can be produced byexposing the polymer to super-critical CO₂ under high temperature andpressure to saturate the polymer with the super-critical CO₂, and thencooling the polymer. Microcellular foams can be produced as described,for example, in U.S. Pat. Nos. 4,473,665 and 5,160,674, which areincorporated herein by reference. The foaming process can be carried outon extruded polymer tube by first dissolving an inert gas such asnitrogen or CO₂ under pressure into the polymer, and then formingmicrovoids by quickly decreasing the solubility of the gas in thepolymer by changing the pressure or temperature, thus inducingthermodynamic instability. Examples of microporous polymeric structuresare disclosed, for example, in U.S. Pat. No. 6,702,849 B1, which isincorporated herein by reference.

Porous Thoralon® can be formed by mixing the polyetherurethane urea, thesurface modifying additive and a particulate substance in a solvent.Preferably the particulate is insoluble in the solvent, and theparticulate may be any of a variety of different particulates or poreforming agents. For example, the solvent may be DMAC, and theparticulate may be an inorganic salt. The composition can contain fromabout 5 wt % to about 40 wt % polymer, and different levels of polymerwithin the range can be used to fine tune the viscosity needed for agiven process. The composition can contain less than 5 wt % polymer forsome spray application embodiments. The particulates can be mixed intothe composition. For example, the mixing can be performed with aspinning blade mixer for about an hour under ambient pressure and in atemperature range of about 18° C. to about 27° C. The entire compositioncan be cast as a sheet, or coated onto an article such as a mandrel or amold. In one example, the composition can be dried to remove thesolvent, and then the dried material can be soaked in distilled water todissolve the particulates and leave pores in the material. In anotherexample, the composition can be coagulated in a bath of distilled water.Since the polymer is insoluble in the water, it will rapidly solidify,trapping some or all of the particulates. The particulates can thendissolve from the polymer, leaving pores in the material. It may bedesirable to use warm water for the extraction, for example water at atemperature of about 60° C. The resulting void-to-volume ratio can besubstantially equal to the ratio of salt volume to the volume of thepolymer plus the salt. The resulting pore diameter can also besubstantially equal to the diameter of the salt grains.

The porous polymer sheet can have a void-to-volume ratio from about 0.40to about 0.90. Preferably the void-to-volume ratio is from about 0.65 toabout 0.80. Void-to-volume ratio is defined as the volume of the poresdivided by the total volume of the polymeric layer including the volumeof the pores. The void-to-volume ratio can be measured using theprotocol described in AAMI (Association for the Advancement of MedicalInstrumentation) VP20-1994, Cardiovascular Implants—Vascular Prosthesissection 8.2.1.2, Method for Gravimetric Determination of Porosity. Thepores in the polymer can have an average pore diameter from about 1micron to about 400 microns. Preferably the average pore diameter isfrom about 1 micron to about 100 microns, and more preferably is fromabout 1 micron to about 10 microns. The average pore diameter ismeasured based on images from a scanning electron microscope (SEM).Formation of porous Thoralon® is described, for example, in U.S. PatentApplication Publication Nos. 2003/0114917 A1 and 2003/0149471 A1, bothof which are incorporated herein by reference.

The prosthetic branch 44 is preferably, but not necessarily, connectedto a branch extension. The prosthetic branch 44 and the branch extension55 preferably have complementary annular crimps 48. Crimping decreasesthe risk of kinking, thereby helping preserve the patency of theprosthesis. Complementary crimping or other types of projections at thetromboning interconnection also help maintain the seal and preventpull-out. Complementary projections on the overlapping modules tend toengage each other to maximize the surface contact between opposingcontact surfaces. The prosthetic branch 44 and the branch extension 55may be only partially crimped.

The crimps shown in FIG. 3a may be created by mounting the prostheticbranch 44, for example, over a mandrel of substantially the samediameter. A thread, wire or other filament is wrapped helically aroundthe prosthetic branch 44. The assembly as described is then heated to atemperature of 138° C. for eight (8) hours. Other temperatures can beused. Typically, the higher the temperature, the shorter the timerequired for adequate crimping, and vice versa. This induces helicalcrimping in the wrapped portion of the prosthesis. Annular crimps canalso be generated by attaching annular filaments to the prostheticbranch 44 and performing the other steps of this process. The crimppeaks can be spaced by any suitable distance, preferably so that thereare about 5 crimp peaks per 10 mm. The crimped interconnection andmethods for producing crimps are described in greater detail in U.S.patent application entitled “Endoluminal Prosthesis WithInterconnectable Modules,” Ser. No. 10/962,001, filed Oct. 8, 2004 (U.S.Patent Application Publication No. 2005/0113905), which is incorporatedherein by reference.

The preferred size and shape of the prosthetic module 40 depends on theanatomy in which it is to be implanted and the corresponding module towhich this prosthetic module 40 will be connected. Physiologicalvariables, deployment characteristics, and other factors also contributeto the determination of proper size and shape of the prosthetic trunk.The prosthetic trunk 42, if designed for deployment into the iliacartery, preferably has a 12 mm diameter through its length, as shown,but may have a taper, turn or any other suitable geometry. Thedimensions of any of the prostheses mentioned herein are only providedas an example, and will preferably be altered to match a particularpatient's anatomy.

The stents 50, 52, 53 maintain the patency of the prosthesis and ensureadequate sealing against the surrounding vascular tissue. One goal forstent design and placement, whether internal or external, is to preventmetal-to-metal contact points, prevent contact between two differenttypes of alloys and minimize micromotion. Stent sizing, spacing anddesign should be determined so that there is no stent-to-stent contacteven in tortuous anatomy. Stents are preferably placed to maximizeprosthesis flexibility while maintaining patency, as well as reducematerial wear and stent fatigue. Furthermore, it is preferable that thestents do not interfere with the prosthetic branch, that they minimizethe potential for galvanic corrosion and ensure adequate jointstability. Stent amplitude, spacing and stagger are preferably optimizedfor each prosthesis design. Any of the stents mentioned herein may havebarbs to help decrease prosthesis migration.

The Z-stent design is preferred for straight sections of the aorta; itprovides both significant radial force as well as some longitudinalsupport. In tortuous anatomy, branches or fenestrations, it may bepreferable to use alternative stents or modifications to the Z-stentdesign to avoid stent-to-stent contact. Furthermore, in complex anatomicsituations, external stents have the potential to become intertwinedwith the wires and other devices utilized to ensure branch vesselaccess, sealing and fixation. In some instance it may be desirable toaffix some of the stents to the internal surface of the prosthesis. TheZ-stents mentioned herein are preferably made from standard medicalgrade stainless steel and are soldered using silver standard solder (0lead/0 tin); other stents may be made from nitinol or other shape-memorymetal.

As shown in FIG. 3a , stents 50, 52, 53 are preferably affixed to theprosthesis 40 both internally 50 and externally 52, 53. PreferablyGianturco-type Z-stents of either 14 or 16 gauge (commercially availablefrom Cook Incorporated, Bloomington, Ind.) are employed, as shown. Thestents 50, 52, 53 are preferably spaced 4 mm from each other, asmeasured peak-to-peak. The peaks 59 are preferably staggered for minimalcontact with each other. The stents 50, 52 preferably have a 14 mmamplitude 41. The stent 53 nearest to the anastomosis 46 has a 22 mmamplitude, except near the anastomosis 46, where the amplitude ispreferably 11 mm so that it does not interfere with the anastomosis 46.This stent 53 may be affixed internally. These stents are preferablyself-expanding, but one or more may be balloon expandable.

At least one stent (not shown) is associated with the prosthetic branch44; it is preferably attached just below the proximal seam 47 of theprosthetic branch 44. The stent is employed to keep the anastomosis 46open and to prevent kinking upon bending of the prosthetic branch 44.Prolene® 5-0 sutures (not shown) are preferably used for the distalsealing stent 50 while polyester 4-0 sutures (not shown) are used forall other stents 52, 53. Two conventional sutures are preferably tied toeach strut 57, and one suture is preferably tied at each peak 59.

The angle of incidence of the prosthetic branch 44 is preferably about20° to about 60°, and more preferably about 45° with respect to theprosthetic trunk 42; the skew is preferably about 0° to about 30° at theanastomosis 46. The prosthetic branch 44 is preferably anchored toprosthetic trunk 42 by three spaced sutures (not shown) no closer thanabout 4 mm from the anastomosis 46.

Standard endoluminal techniques may be used to deploy this prosthesis,as described below in further detail. An 18 French sheath may be used,unless loading issues warrant a larger sheath such as a 20 French.Standard radiopaque gold markers (Cook Incorporated, Bloomington, Ind.)are preferably used to assist graft orientation when the prosthesis isviewed through a fluoroscope.

FIG. 3b is an alternative perspective of the prosthesis 40 of FIG. 3a .This shows the shape of the anastomosis 46. The size and shape of theanastomosis 46 may promote laminar flow and other positive hemodynamiccharacteristics. One method for creating this kind of anastomosis isdescribed below in reference to FIG. 5.

After the prosthesis 40 is implanted, the distal ostium 54 of theprosthetic branch 44 is preferably positioned in the vicinity of themain vessel-branch vessel anastomosis. Then the branch extension 55,shown in FIG. 3c , can be implanted so that it forms a tromboningconnection with the prosthetic branch 44. There is preferably a 1 mm orless difference in diameter at the interconnection between the distalostium 54 of the prosthetic branch 44 and the branch extension 55 toencourage a sealing interconnection. The branch extension 55 may havestents, preferably internal stents, which are less likely to interferewith the seal or fit between corresponding crimps 48. The branchextension 55 can also be a properly sized Viabahn® Endoprosthesis (W. L.Gore & Associates, Inc., Newark, Del.), a Fluency® self-expandingnitinol stent graft (Bard, Tempe, Ariz.) or an iCast® covered stent(Atrium, Hudson, N.H.). One or both ends of the branch extension canhave a nitinol ring or coil; a proximal ring or coil preferably engagesa corresponding nitinol ring or coil in the helical branch of FIG. 17.The stent can be covered, uncovered or partially covered with PTFE,ePTFE, woven polyester, Thoralon® or other materials. The stents may beself-expanding or balloon-expandable.

FIG. 4a shows a top view of a prosthesis 60 with a prosthetic trunk 62and prosthetic branch 64. This prosthesis 60 is designed to be deployedinto the right common iliac artery and branch to the right hypogastricartery, although can be adapted for deployment into other vessels. Theprosthetic branch 64 is positioned longitudinally along andcircumferentially about an external surface of the prosthetic trunk 62,i.e. generally in the form of a helix about the longitudinal axis 75.The prosthetic branch 64 shown in FIG. 4a makes a 195° (or slightly morethan one-half the circumference) turn about the prosthetic trunk 62 asmeasured from the midpoint 77 of the anastomosis to the midpoint of thedistal ostium 65, as shown in FIG. 4a . This perspective shows that thedistal ostium 65 of the prosthetic branch 64 is beveled by 30°. This mayincrease the access angle and ease of insertion for the branchextension. A side view of the prosthesis 60 of FIG. 4a is shown in FIGS.4b and 4c . This prosthesis 60 has three external Z-stents 66 near theprosthetic trunk 62. FIG. 4c , a skeletal view of the prosthesis, showsan internal Z-stent 70 that straddles the anastomosis 68 and an internalstent 72 on the distal terminus 74. One method for forming the enlargedanastomosis 68 is shown in FIGS. 5a-d . The Z-stent 70 that is adjacentthe anastomosis may be attached to the graft internally or externally.The flexibility of the prosthetic trunk 62 may be increased by annularor helical crimping of the fabric between the stents of the prosthetictrunk 62.

FIG. 5a shows a process for creating an enlarged or “tear-drop”anastomosis. The starting material for the prosthetic branch 80 istypically a tubular section of polyester prosthesis fabric. The tubularlength of prosthesis fabric may also be flared towards the proximal end84. The proximal end 84 of the prosthetic branch 80 can be cut at aright angle to the longitudinal axis of the prosthetic branch 80, asshown, or can be beveled or otherwise shaped. The prosthetic branch 80is cut along a line 82 at its proximal end 84. The line 82 does not haveto be parallel to the axis of the tube. Then, as shown in FIG. 5b , theproximal end 84 is splayed. Following splaying, the proximal end 84 canbe further shaped to form a new perimeter 86, as shown in FIG. 5c . Thesplayed perimeter 89 of the proximal end 84 shown in FIG. 5b ispreferably sewn to the perimeter of a fenestration (not shown) in theprosthetic trunk 88 of a shape and size to match the splayed perimeter89, as shown in FIG. 5d . The seam is preferably blood-tight. Thefenestration can be oriented in any way relative to the axis of theprosthetic trunk 88 to skew the prosthetic branch 80. The prostheticbranch 80 is then preferably attached to the prosthetic trunk 88 suchthat it is positioned longitudinally and circumferentially in relationto the prosthetic trunk 88.

FIG. 6a shows a prosthesis 90 with two helical peripheral prostheticbranches 92, 94 extending therefrom. This prosthesis is designed to bepositioned within the aorta so that the prosthetic branches 92, 94 canextend to the renal arteries, although this prosthesis design can beadapted for use in other vessels. Branch extensions can then bepositioned within the renal arteries so that they form a tromboningconnection with the prosthetic branches 92, 94. The uncovered stent 96is a suprarenal fixation stent which may have barbs (not shown). Askeletal view of the prosthesis 90 of FIG. 6a is shown in FIG. 6b . Thestent 95 closest to the distal end 93 of the prosthesis 90 is preferablyattached internally, as is the stent 97 near the anastomoses 98. Theanastomoses 98 can be as shown or can be the enlarged anastomosisdescribed above with reference to FIG. 5. The prosthetic branches 92, 94may slope away from the distal end 93 of the prosthesis 90, as shown, ortowards the distal end 93 of the prosthesis 90. Stents (not shown) maybe used to keep the prosthetic branches 92, 94 patent. Additionalprosthetic branches may be anastomosed to the prosthesis 90 to shuntblood to the celiac, SMA, and/or other branch vessels.

In FIG. 7a , a skeletal view of a prosthesis 110 with a helicalcontralateral prosthetic branch 112 is shown. The prosthesis 110 isdesigned for deployment into a right iliac artery and branching into thehypogastric. Distally to the bifurcation 116, the length of theprosthetic branch 112 is positioned longitudinally and circumferentiallywith respect to the prosthetic trunk 114 and is seamless along itslength. The longitudinal and circumferential placement of the prostheticbranch 112 is secured with one or more sutures (not shown) near and moreproximally from the distal ostium 120 of the prosthetic branch 112. Forthis and other prostheses, the prosthetic branch 112 may extend into theprosthetic trunk 114, proximally to the bifurcation 116, such that thebranch lumen (not shown) originates within the lumen (not shown) of theprosthetic trunk 114.

The prosthesis 110 is preferably made from woven polyester describedabove; the prosthetic branch 112 is preferably crimped. The stents areattached using Prolene® 5-0 sutures. Gold markers (not shown) arepreferably attached to the prosthesis 110 in various locations toindicate the position and orientation of the prosthesis 110 under afluoroscope.

An internal stent 123 is used in the prosthetic branch 112 slightlybelow the seam 118 and near the bifurcation 116 to keep the prostheticbranch 112 patent and prevent kinking; this stent 123 is preferablyinternal to the prosthesis 110, but can also be placed externally. Thestent 123 is preferably 6 gauge in diameter, has an amplitude of 8 mmand a period of 6. Two prosthetic trunk stents 126 are attachedproximally to the bifurcation 116; these stents 126 preferably have a 17mm amplitude, a diameter of 20 gauge and a period of 9. The prosthesis110 also has four stents 128 placed distally to the bifurcation 116;these stents 128 preferably have a 14 mm amplitude, a diameter of 14gauge and a period of 7. The stents 126, 128 are spaced about 4 mm fromeach other and the peaks 127 of the distal stents 128 are staggered tominimize contact between them. The two most distal stents 125 on theprosthetic trunk 114 can be affixed internally to prevent interferencewith the deployment of the branch extension.

The distal ostium 120 of the prosthetic branch 112 is preferably 6 mm indiameter. The distal end 122 of the prosthetic trunk 114 is preferably14 mm in diameter; the proximal ostium 130 of the prosthetic trunk 114is preferably 20 mm in diameter. The diameter of the prosthetic trunk114 may be reduced to 12 mm. The distance between the proximal end 124of the prosthetic trunk 114 to the distal end 132 of the prostheticbranch 112 is preferably about 65 mm. These dimensions are only providedas an example and may be varied to match the anatomy of a specificpatient.

FIG. 7b shows a top view of the prosthesis of FIG. 7a . The prostheticbranch 112 preferably turns 151° about the longitudinal axis 139 of theprosthetic trunk 114.

FIGS. 8a-d show different perspectives of a contralateral branchedprosthesis 140 similar to the branched prosthesis described in FIGS.7a-b . This prosthesis 140 is designed for deployment into a right iliacartery and branching into the right hypogastric. Radiopaque markers 142are sewn to the prosthesis 140. The prosthetic branch 144 is preferablymade of woven, crimped polyester. In FIG. 8d , the seam 146 between theprosthetic branch 144 and the prosthetic trunk 141 is evident. The stent(not shown) nearest to the distal end 145 of the prosthetic trunk 141 isattached internally. Any or all of the external stents 143 positioneddistally to the seam 146 may be moved internally. Also, the prostheticbranch 144 at the seam 146 could be beveled; this would provide a largerostium.

FIGS. 9a-b show an additional embodiment of the contralateral branchedprosthesis similar to that described in reference to FIG. 7. FIG. 9a isa skeletal view, showing both the internal stent 160 and the externalstents 162. The prosthesis of FIG. 9 has a prosthetic branch 161 thatextends vertically down from the bifurcation 168 and then bends aroundthe prosthetic trunk 170. The second-most distal stent 163 can also beaffixed internally.

FIGS. 10a-b are schematic representations of the prosthesis described inreference to FIGS. 11a-c , below, and show another embodiment of acontralateral branched prosthesis 210. This prosthesis 210 is designedfor deployment into the common iliac and branching into the hypogastric,although it can be adapted for use in any branched vessel. Thelongitudinal and circumferential placement of the prosthetic branch 212is secured with one or more sutures near the distal end 220 of theprosthetic branch 212 and more proximally from the distal end 220. Theprosthesis 210 is preferably made from woven polyester; the prostheticbranch 212 is preferably made from crimped polyester. FIG. 10b shows therelative orientation of the prosthetic branch 212 to the prosthetictrunk 214; the prosthetic branch 212 preferably turns 151° helicallyaround the prosthetic trunk 214.

FIGS. 11a-c show a branched contralateral prosthesis 211 suitable fordeployment within the right iliac artery and branching into thehypogastric artery. The prosthetic trunk 233 has a proximal section 217with a diameter of about 20 mm and a distal section 219 with a diameterof about 12 mm. The prosthetic branch 213 originates at the 20 mmdiameter proximal section 217 and has a helical path about the 12 mmdistal section 219. The helical path of the prosthetic branch 213 isapproximately 180° in circumference and approximately 60 mmlongitudinally from the seam 225. The pitch is preferably about 45°. Theprosthetic branch 213 is preferably 6 mm in diameter through its lengthand constructed of crimped polyester graft material.

An internal stent 223, shown in FIG. 11a , slightly overlaps the seam225 so that it is flush with the bifurcation 227 to keep the ostium openand prevent kinking upon bending of the prosthetic branch 213. Thisstent 223 is preferably attached to the internal surface of theprosthesis 211, but can also be placed externally. The stent 223 ispreferably 6 gauge in thickness, 8 mm in height and preferably has aperiod of 6. Two stents 226 are attached proximally to the bifurcation227; these stents 226 preferably have an 18 mm amplitude, a diameter of20 gauge and a period of 10, and are spaced from each other by 2 mm. Theprosthesis 211 also has four stents 228 placed distally to thebifurcation 227; these stents 228 have a preferred 14 gauge thickness,14 mm amplitude, a period of 7, and are spaced by 3 mm. The two mostdistal stents 229 are preferably attached internally. The stents arepreferably attached using Prolene® 5-0. Gold markers 215 are attached tothe prosthesis 211 in various locations to indicate the position of theprosthesis 211 under a fluoroscope.

The distal ostium 220 of the prosthetic branch 213 is preferably 6 mm indiameter; the distal end 222 of the prosthetic trunk 214 is preferably12 mm in diameter; the proximal ostium 230 of the prosthetic trunk 214is preferably 20 mm in diameter. The dimensions of this prosthesis 211,like the other prostheses described herein, are preferably matched tothe anatomy of a specific patient. The peaks 231 of the prosthetic trunkstents 226, 228 are staggered to minimize contact between them. Thedistance between the proximal end 224 of the prosthetic trunk 214 to thedistal ostium 222 of the prosthetic branch 212 is preferably about 70mm. Deployment of this prosthesis 211 is made easier by the helicaldesign, which allows the “angle of access” to be about 3 times greaterthan in y- or t-shaped branched prostheses.

FIG. 12a shows a skeletal view of a peripheral branched prosthesis 250.The prosthetic branch 252 of this prosthesis 250 extends at an anglefrom the side of the prosthetic trunk 254 and then bends back to theprosthetic trunk 254 where it is affixed with sutures. There is a gap256 between the prosthetic branch 252 and the prosthetic trunk 254. Theprosthetic branch 252 is preferably crimped (not shown), seamless andabout 6 mm in diameter through its length. The prosthetic trunk 254 isseamless and about 12 mm in diameter through its length. The prostheticbranch 252 is anastomosed to the prosthetic trunk 254 between first 253and second 255 proximal stents.

FIG. 12b is an external view of the prosthesis of FIG. 12a . As shown,only the top two stents 253, 255 are attached externally to theprosthesis 250. The other stents shown in FIG. 12a are attachedinternally. The stents 253, 255 that are around the anastomosis 259 maybe affixed internally so that they do not catch on guide wires (notshown) used in deployment of the prosthesis 250. FIG. 12c shows a topview of the prosthesis of FIGS. 12a and 12b . The prosthetic branch 252turns 137° around the prosthetic trunk 254, and is attached to theprosthetic trunk 254 at a location 261.

An external view of a peripheral branched prosthesis 300 is shown inFIG. 13a . The prosthetic trunk 302 and the prosthetic branch 304 areboth preferably made from polyester. The prosthetic branch 304 ispreferably crimped (not shown) and seamless. Z-stents 306 of both 14 mmand 22 mm amplitudes are preferably attached to the prosthesis 300 withsutures (not shown). Prolene® 5-0 is used to attach the internal distalstents 312, shown in FIG. 13b ; polyester 4-0 is used to attach theproximal stents 310. There are preferably crimps 301 between the stents306 of the prosthetic trunk 302; these may increase flexibility anddecrease kinking of the trunk 302. Gold markers (not shown) may beemployed. A nitinol ring or coil may be attached to the prosthetic trunk302 above the Z-stents; a corresponding nitinol ring or coil ispreferably attached to the distal section of the leg to which theperipheral branched prosthesis 300 can mate.

The prosthetic trunk 302 is preferably straight, having a consistent 12mm diameter throughout. The stent 314 that abuts the prosthetic branch302 has an amplitude of 22 mm, except as shown in FIG. 13b where theamplitude is 11 mm near the anastomosis 320. This stent 314 ispreferably attached externally, as shown; it may be affixed internally.The angle of incidence of the prosthetic branch 304 to the prosthetictrunk 302 at the anastomosis 320 can range from about 20° to about 60°,and is preferably about 45°; the skew relative to the longitudinal axis324 is preferably between about 0° to about 20° and more preferablyabout 0°. The length of the prosthetic branch 304 is adjacent to theprosthetic trunk 302; this may improve the distribution of material toreduce packing density during deployment of the prosthesis 300. Theprosthetic branch 304 is anchored to prosthetic trunk 302 about 4 mmfrom the anastomosis 320 using about three sutures; they may be affixedfurther away to ensure the flexibility of the anastomosis 320.

The most proximal stent 322 is preferably of a 14 mm amplitude andattached externally to the prosthesis 300. The material underneath themost proximal stent 322 is crimped for superior mating to a proximalprosthesis; this stent 322 may also be attached to the inside surface ofthe prosthesis 300. The enlarged anastomosis 320 described above inreference to FIG. 5 is used to connect the prosthetic branch 304 to theprosthetic trunk 302. The three distal stents 312 are attachedinternally.

FIG. 13c shows a top view of the prosthesis of FIGS. 13a-b . Theprosthetic branch 304 preferably wraps about 150° around the prosthetictrunk 302. The distal ostium 330 of the prosthetic branch 304 ispreferably beveled about 30°.

FIGS. 14a-b show a prosthesis 350 that is similar to that described inreference to FIG. 13. The prosthetic branch 352 is preferably made fromcrimped polyester fabric. The region under the proximal stent 358 iscrimped. The anastomosis 354 is preferably enlarged, as described abovein reference to FIG. 5. The prosthetic branch 352 is skewed relative tothe longitudinal axis 356 of the prosthesis 350 and has an angle ofincidence preferably of about 30° to about 40°. The bevel of theprosthetic branch 352 is may be trimmed to provide greater clearance forthe top stent 358.

FIG. 15a shows a schematic representation of a bifurcated endoluminalprosthesis 400 implanted into an aneurysmal aorta 402. An example of abifurcated endoluminal prosthesis 400 is the Zenith® AAA stent graft(Cook Incorporated, Bloomington, Ind.). The prosthesis 400 extends intothe iliac arteries 404, 405. One of the iliac limbs 407 forms atromboning interconnection with an iliac extension 409, which, in thiscontext is the prosthetic trunk. The iliac extension (i.e. prosthetictrunk) 409 is anastomosed to a helical prosthetic branch 408. Thehelical prosthetic branch 408 forms a tromboning interconnection withthe hypogastric branch extension 410 which sits in the hypogastricartery 406. The helical prosthetic branch 408 may also curve around theother side (posterior side) of the iliac extension 409.

In FIG. 15b , there is a modular prosthesis that is similar to thatshown in FIG. 15a . However, the iliac extension 409 of FIG. 15b isconnected to the iliac leg 407 via an intervening prosthetic module 403.An example of an intervening prosthetic module 413 is shown in FIG. 15c. The distal end 423 of the intervening prosthetic module 413 is crimpedand has an internal stent 420. External stents 422 are attached to theoutside of the module 413. The intervening prosthetic module 403 ispreferably deployed after the aortic stent graft 400 and the iliacextension 409 are deployed, so that the intervening prosthetic module403 is overlapped on both ends. The crimps on the distal end 423preferably engage corresponding crimps on the proximal end of the iliacextension 409. Either the aortic graft 400 or the iliac extension 409may be deployed first.

It may be preferable to support the prosthetic branch with one or morestents. As shown in FIG. 16, the prosthetic branch 414 has annularstents 415. These stents 415 are preferably made of stainless steel, ornitinol wire or other shape memory metal. Any suitable thickness of wiremay be used, preferably of a diameter of about 0.006-0.009 inch. Thestents 415 can be either closed loop rings or coils with free ends, andcan be attached using sutures or other suitable method. They can bepositioned at various intervals from a location near the trunk 412 tothe distal ostium 416. FIG. 17 shows an annular stent 415 affixed to thedistal ostium 416 of the branch prosthesis 414 using sutures 417.

As shown in FIG. 18, a helical stent 418 can also be used to support thehelical branch 414. The helical stent 418 is preferably made fromnitinol or other shape memory metal. Any suitable thickness of wire maybe used, preferably having an outer diameter of about 0.006-0.009 inch.As shown in FIG. 19, an end of the helical stent 418 can be formed intoa closed loop 419 so that it supports the distal ostium 416 of thebranch 414. FIG. 20 shows a nitinol coil that is attached to theproximal ostium of the branch 414 to hold the ostium in its operationalstate.

FIGS. 21a-d show two, preferably endless, Z-stents that have tworegions: the zigzag region 437 which encircles the tubular graft and asection designed to accommodate and/or support at least a portion of thebranch-trunk anastomosis. The stent of FIG. 21a has a section 438 thatis shaped to support the proximal aspect of the anastomosis. The stentof FIG. 21b has a section 439 that is shaped to support the distalaspect of the anastomosis. The stents of FIGS. 21a-b are shown workingto support a branch-trunk anastomosis in FIG. 22 a.

As shown in FIG. 22a , the endless Z-stents are attached to theprosthetic trunk; each stent is curved around one of two differentportions of a perimeter of the anastomosis. The stents of FIG. 21a mayalso be placed on the distal aspect of the anastomosis, which the stentof FIG. 21b is placed on the proximal aspect of the anastomosis. FIG.22b shows a stent similar to that shown in FIG. 21c attached to a stentgraft.

FIG. 21c shows a Z-stent 437 that contains a loop 440 that is designedto follow the perimeter of the branch-trunk anastomosis. FIG. 21d has asection 441 that is shaped to support the distal aspect of theanastomosis.

FIGS. 23a-d show a stent that is designed to maintain the shape of thebranch-trunk anastomosis. The stent 470 has three main portions, adistal hoop 472, a proximal hoop 471 and an ovoid outer stent perimeter473. FIG. 23e shows the stent 470 attached internally to a branch-trunkanastomosis. The stent 470 may be attached in any conventional manner,including sutures. The ovoid outer perimeter 473 is preferably suturedto the prosthetic trunk, while the hoops 471, 472 extend away from theperimeter 473 into the prosthetic branch, and is preferably sutured tothe prosthetic branch. The stent 470 preferably maintains the shape ofthe anastomosis.

The stent of FIGS. 23a-f is preferably made from a single nitinol wireor similar shape-memory metal. To have the wire “remember” the shapedepicted in FIGS. 23a-e , the wire is preferably heat-set while in thatshape. This can be accomplished through the use of the device 474 ofFIGS. 24a-d or a similar heat-setting fixture or mold. A plan view ofthe fixture 474 is shown in FIG. 24b . The ovoid outer perimeter 473 isformed by wrapping the nitinol wire around the column 486. The distalhoop 472 is formed by looping the wire over the distal arch section 485of the base 483; the proximal hoop 471 is formed by looping the wireover the proximal arch section 484 of the base 483. The hoops 471, 472kept in place by the arched surfaces 478, 479 on the fixture cavity 481when the fixture cavity 481 is attached to the base 483. The base 483 isattached by a screw or bolt that passes through the hole 480 and intothe column 486.

For prosthetic trunks designed for implantation into the aorta,prosthetic branches may be formed to shunt flow into the superiormesenteric, celiac and both renal arteries. There are a variety ofpossible arrangements and orientations for these multiple branches, asshown in FIGS. 25 through 27. FIG. 25 shows an aortic module 520 havingtwo renal branches 524, 525, both of which shunt flow proximallyrelative to the prosthetic trunk. In FIG. 25, both the celiac branch 522and the SMA branch 521 shunt flow distally relative to the prosthetictrunk. As shown in FIG. 26, the celiac branch 523 can be positioned sothat it extends proximally.

As shown in FIG. 27a , the celiac branch 526 can extend distally fromthe same side of the trunk 520 as the SMA branch 521. The renal branchescan also be positioned so that they extend distally. FIG. 27b hashelical renal branches 524, 525 that extend proximally relative to theprosthetic trunk 520. The celiac 533 and SMA 534 branches share a commonanastomosis 519 before splitting to their respective vessels. FIG. 27cshows an arrangement for the renal branches 538, 539 having a commonanastomosis 535.

In FIG. 27d , the prosthesis has celiac and SMA branches 533, 534 influid communication with the prosthetic trunk 520 through a commonanastomosis 519 formed in the wall of the prosthetic trunk. In thisexample, the celiac branch 533 is in fluid communication with the SMAbranch 534 through an anastomosis 537 formed in the wall of the SMAbranch. Thus, the celiac branch inlet end is separate, and disposeddownstream, from the SMA branch inlet end.

One advantage of decoupling the inlet ends of the branches 533, 534 isthat the size of the trunk anastomosis 519 may be reduced. This mayreduce the amount of graft material at the anastomosis 519 and thepacking density of the graft within the delivery sheath. For example,two prostheses may be constructed, each having celiac and SMA branches533, 534 that share a common anastomosis 519, as shown in FIG. 27b . Inthis example, the distal ends of the celiac and SMA branches 533, 534each have a diameter of 8 mm. In the first graft, the celiac and SMAbranches 533, 534 are constructed so that they bifurcate adjacent theanastomosis 519 into branches, each having a diameter of approximately 8mm. The first graft is constructed with an anastomosis 519 that is largeenough to accommodate the size of the inlet ends of both branches 533,534, for example, approximately 16 mm.

The second graft is constructed with the inlet ends of the branches 533,534 decoupled as shown, for example, in FIGS. 27d and 27e . Theanastomosis 519 need only be large enough to accommodate the inlet endof the SMA branch 534 and, therefore, it may be possible to constructthe second graft with a substantially smaller anastomosis 519 withoutcompromising fluid flow. For example, the second graft may have ananastomosis 519 with a diameter of approximately 10 mm. The diameter ofthe SMA branch 534 may taper along its length, as shown in FIG. 27 e.

It should be understood that this example is illustrative, rather thanlimiting, and that the absolute and relative dimensions of the graftsand components of the grafts can vary. For example, the anastomosis 519in the first graft described above may have a diameter that is less thanor greater than 16 mm. Likewise, the anastomosis 519 in the second graftdescribed above may have a diameter that is less than or greater than 10mm.

At least one of the branches 533, 534 may be disposed longitudinallyalong and circumferentially about the trunk 520, as shown in FIGS. 27band 27d . FIG. 27e shows an example of a prosthesis where the celiacbranch 533 is disposed longitudinally along and circumferentially aboutthe SMA branch 534. The size, configuration, and orientation of thebranches will be determined based on various considerations, asdiscussed throughout the specification, such as patient anatomy andpromoting laminar flow.

Any of the branches can be oriented so that they extend proximally ordistally; similarly, any of the branches can be positioned on eitherside of the trunk. The arrangements may be chosen in response to patientanatomy, as well as deployment and functional considerations.

FIG. 28a shows an internal helical branch 528, extendingcircumferentially around and longitudinally about an internal surface ofthe prosthetic trunk 527, terminating at the distal ostium 529. As shownin FIG. 28b , this approach may cause turbulent flow, especially wherethe internal branch 528 is at an angle to the blood flow. To improveflow characteristics, the internal branch 528 can be straddled bybaffles 530, 531, as shown in FIG. 29. These baffles 530, 531 may bemade of any of the materials listed above, and function by filling in orcovering the gaps 532 on either side of the branch 528, where itcontacts the trunk 527. Baffles preferably act to deflect the flowaround portions of the internal helical branch that are at an angle tothe direction of blood flow, so that the blood flow is less turbulent.

Another solution to the turbulent flow around the internal branch 528 isthe inclusion of the branch 528 within a pocket 536, as shown in bothFIGS. 30 and 31. The cross-section depicted in FIG. 31 shows morelaminar flow along the pocket 536 where the internal helical branch runsat an angle to the direction of blood flow. The pocket 536 may be madefrom woven polyester twill, as described above, or any other suitablematerial. The internal branch is preferably stented so that it remainspatent. The stents may be similar to those stents described and shown inregard to external helical branches. An internal figure-8 Z-stent 535shown in FIG. 28c may also be used to keep both the branch lumen 533 andthe trunk lumen 534 patent. The figure-8 stent 535 is preferably madefrom a single length of stainless steel wire.

To facilitate deployment of a prosthetic extension module into aprosthetic branch, it may be necessary to have a preloaded wire extendfrom the inside of the main prosthesis through the prosthetic branch.Depending on the configuration of the prosthetic branch, such a wire mayhave to bend excessively (i.e., have a small radius bend) as it passesfrom the main body of the prosthesis into the prosthetic branch. Thissituation may cause damage to the wire or the prosthesis, or impededeployment. As shown in FIG. 32a , an enlarged anastomosis 541 betweenthe prosthetic trunk 540 and prosthetic branch 545 may enable thedeployment wire 543 to have a bend of a larger radius.

An enlarged anastomosis 541 of this type may be especially important inthe side branch vessels of the aortic arch, including the leftsubclavian, left common carotid and innominate arteries. A helicalbranch 545 extending into the innominate artery, which has a tailsection to accommodate the guide wire, is shown in FIG. 32a . The sizeof the anastomosis 541 may be measured relative to the radius of theprosthetic branch 545. The radius of the anastomosis 541 may be twicethat (or more) of the average radius of the prosthetic branch 545 or thedistal ostium 546 of the branch 545. The anastomosis 541 shown in FIG.32a is enlarged by the addition of a tail section 542 through which thewire 543 can travel, which also increases the radius of the turn. Ananastomosis with a tail section will be understood as being ananastomosis that has both a wide section and a narrow section, thenarrow section being the tail. The thoracic aortic stent graft of FIG.32a may also extend further into the abdominal aorta, having some of thebranches and/or fenestrations described elsewhere in this application.The tailed anastomosis can also be used to increase the guidewire's turnradius in Y-shaped side branches.

FIGS. 32b and c show various arrangements for the thoracic side branchesthat extend from the prosthetic trunk 540. The enlarged anastomosisshown in FIG. 32a may also be used in the thoracic prosthetic branchesshown in FIGS. 32b and c . In FIG. 32b , there are separate helical sidebranches 547, 567, 569 for the innominate, left common carotid, and leftsubclavian, respectively. The arch grafts are preferably curved toaccommodate the curve of the aortic arch. FIG. 32c shows the left commoncarotid prosthetic branch 551 and left subclavian prosthetic branch 553having a common anastomosis 548. Any of the branches shown in FIGS.32a-c may be selectively replaced by fenestrations.

FIG. 32c has proximal strain relief crimps 579 and distal strain reliefcrimps 581 in the prosthetic trunk 540. These are selectively placed onthe ends of the prosthetic trunk 540 to provide some strain relief asthe thoracic aorta undergoes axial compression and extension under theinfluence of pulsatile flow. The crimps 579, 581 allow the graft to moreeasily lengthen, shorten and bend in tandem with the thoracic aorta. Thedistal 582 and proximal 583 stents improve sealing at the ends of thetrunk 540, and may also have barbs (not shown) to enhance fixation.

Blood flow to the various branch vessels of the aorta or other vesselmay be accommodated through use of any combination of fenestrations andprosthetic branches, including the integral helical branches describedabove. One such combination is shown in FIGS. 33 through 40. FIGS. 33through 40 show various views of an endoluminal prosthesis 549 that hasa helical prosthetic branch 552 for shunting flow to one of the renalarteries, a contralateral renal fenestration 558 (an aperture in thewall of the prosthesis that allows blood to flow to one of the renalarteries) and a superior mesenteric artery fenestration 556 (an aperturein the wall of the prosthesis that allows blood to flow to the SMA). Aflareable covered or uncovered stent may be deployed into either or bothfenestrations 556, 558 in the manner described in U.S. patentapplication Ser. Nos. 10/984,040; 10/984,416; 10/984,417; 10/984,131;10/984,520; and 10/984,167, all of which were filed on Nov. 8, 2004 andall of which are incorporated herein by reference.

FIG. 33 shows the helical branch 552 extending proximally along atapered prosthetic trunk 550 relative to the prosthetic trunk 550, i.e.,away from the distal end 555 of the prosthesis 549. As shown, thehelical branch 552 has a pitch (or skew) of about 44° relative to thelongitudinal axis of the prosthetic trunk 550 and is preferably attachedwith six evenly space sutures. The branch 552 is preferably notstretched or compressed when sutured to the trunk 550. Radiopaquemarkers 557, 559 are attached to both the trunk 550 and the branch 552.The radiopaque markers 559 on the trunk 550 are preferably aligned withthe longitudinal axis of the trunk 550. A suprarenal stent 562 islocated at the proximal end 562 of the prosthesis 549; this stent ispreferably a Z-stent having a diameter of 32 mm, a height of 25 mm and aperiod of 10. The SMA fenestration 556 is visible in FIG. 33. Afenestration may also be provided for the celiac artery in addition toor instead of the SMA fenestration. The helical branch 552 is preferablycrimped (not shown) to help resist kinking.

FIGS. 34 through 36 show the same device in different rotations. FIG. 34shows the relative orientation of the renal fenestration 558 and the SMAfenestration 556. The relative orientation of the branch and thefenestrations can be modified to suit a particular patient's anatomy.FIG. 35 shows the enlarged anastomosis 564 between the branch 552 andthe trunk 550. FIG. 36 shows the beveled ostium 565 of the branch 552.

FIGS. 37 and 38 show skeletal views of the device depicted in FIGS. 33through 36; the distal internal stents 559 and proximal internal stents560 are visible in these figures. The distal internal stents 559 arepreferably Z-stents having a diameter of 24 mm, a height of 14 mm and aperiod 10. The proximal internal stents 560 are preferably Z-stentshaving a diameter of 32 mm, a height of 22 mm and a period of 12. Theouter stents 561 are preferably Z-stents having dual amplitude, adiameter of 32 mm, a height of 17 mm at a period of 11, and a height of8.5 mm at a period of 22; these stents 561 are preferably made ofnitinol wire having an outer diameter of about 0.330 mm. Any of thesedimensions can be tailored to a particular patient's anatomy. FIG. 39shows a view in the direction of arrow “A” shown in FIG. 38; FIG. 40shows a view in the direction of arrow “B” shown in FIG. 38.

FIGS. 41a-d show different views of a stent graft 600 having a helicalprosthetic branch 614 and three fenestrations: a left renal fenestration606, a right renal fenestration 636 and an auxiliary fenestration 604.The helical branch 614 feeds the SMA and extends longitudinally andcircumferentially from the enlarged anastomosis 622. The proximal end630 of the stent graft 600 also has a scallop 630 to accommodate theceliac artery. By combining one or more fenestrations with one or morehelical branches, flow to one or more of the branch vessels may bepreserved while optimizing the deployment characteristics of the stentgraft system and packing profile of the stent graft within thedeployment sheath.

Radiopaque markers 602, 612 near the proximal 626 and distal 624 ends ofthe stent graft 600 help the surgeon identify the rotation of the stentgraft 600 during deployment, as do the markers 620 on the helical branch614. The helical branch 614 may have a beveled distal anastomosis 618.The stent graft 600 is supported by both externally placed stents 610near the proximal end 626 of the stent graft 600 and internally placedstents 608. As shown in FIG. 41c , regions 632, 634 near the anastomosis622 may be occupied by stents of any shape, preferably those designed toavoid obstructing and support the anastomosis 622, such as those ofFIGS. 21a-d . FIG. 41d shows an axial view of the stent graft 600 fromthe distal end 624.

FIGS. 42a-d show another stent graft 650 that has both fenestrations anda helical branch graft. This stent graft 650 has a taper 670 in themiddle such that the diameter is smaller at the distal end 656 andthrough the distal section 668 than at its proximal end 658 and throughits proximal section 666. There are three fenestrations in the graft, anSMA fenestration 662, a left renal fenestration 664, and a right renalfenestration 672. The helical branch 660 provides flow to the celiacartery. The stent graft 650 is supported by external Z-stents 654 andinternal Z-stents 676. The taper 670 may by supported by stents of anyshape, preferably those designed to avoid obstructing the branch-trunkanastomosis 670, such as those of FIGS. 21a-d . There is an uncoveredproximal stent 652 which preferably has barbs (not shown) extending fromit to enhance fixation.

Since arterial anatomy and aneurysm topology vary between patients, anyof the prosthesis designs described above is preferably modified toaccommodate a particular patient's need. The first step is to review thepatient's CT scans. The critical parameters for prosthesis design(deployment site, proximal and distal sealing points) for the deviceneeded for each patient are defined. A three-dimensional (3-D) model ofthe aneurysm is created using techniques known to one of skill in theart.

The aneurysm model can be incorporated into Solid Works™ or othersuitable solid and surface modeling software. With this software a 3-Dendoluminal prosthesis can be designed based on the aneurysm model andthe defined critical parameters. A mechanical drawing is developed fromthe 3-D device. The mechanical drawing specifications are then used tocreate the component materials for the prototype prosthesis, includingthe prosthesis fabric and stents. Then the material and stents areassembled to form the final prosthesis.

A Modular Prosthesis and Introducer

Modular prostheses are known for use in treating descending thoracic andabdominal aortic aneurysms, where the prosthesis at the proximal enddefines a single lumen for placement within the aorta and at the otherend is bifurcated for extension into the iliac arteries. Iliac extensionprosthetic modules can be connected to the ends of the bifurcation. Aschematic view of such a prosthesis is described in further detail inPCT application WO98/53761.

WO98/53761 discloses a prosthesis which includes a sleeve or tube ofbiocompatible prosthesis material such as polyester fabric orpolytetrafluoroethylene (PTFE) defining a single-lumen portion and abifurcation, and further includes several stents secured therealong. Theprosthesis is designed to span an aneurysm that extends along the aortaproximally from the two iliac arteries. This reference also disclosesthe manner of deploying the stent prosthesis in the patient utilizing anintroducer assembly.

In the WO98/53761 application, the material-covered portion of thesingle-lumen proximal end of the prosthesis bears against the wall ofthe aorta above the aneurysm to seal the aneurysm at a location that isspaced distally of the entrances to the renal arteries. Thin wire strutsof a proximal attachment stent traverse the renal artery entranceswithout occluding them, while anchoring the prosthesis in positionwithin the aorta.

An extension module is affixed to one of the legs of the prosthesis toextend along a respective iliac artery and, optionally, extensions maybe affixed to both legs. These extension modules are attached bytromboning. The deployment of a modular endoluminal prosthesis into thelumen of a patient from a remote location by the use of a deploymentdevice or introducer is disclosed in the same patent application. PCTapplication WO98/53761 is incorporated herein by reference.

One modular prosthesis similar to that described in WO98/53761, theZenith® AAA Endovascular Graft sold by Cook Incorporated, has beenapproved by the Food and Drug Administration (FDA) to treat aorticaneurysms. The Zenith® AAA Endovascular Graft is made up of threeprosthetic modules: a main body module and two leg modules. The mainbody is positioned in the aorta. The legs are positioned in the iliacarteries and connect to the main body. The prosthesis thus extends fromthe aorta below the renal arteries into both iliac arteries. Theprosthesis itself is made of a polyester material like that used in opensurgical repair. Standard surgical suturing techniques are used to sewthe graft material to a frame of stainless steel stents. Theseself-expanding stents provide support for the graft material.

FIG. 43 shows a Zenith® self-expanding bifurcated prosthesis 720(product code TFB1 through TFB5, available from Cook Incorporated,Bloomington, Ind.), and an endovascular deployment system 700, alsoknown as an introducer 700, for deploying the prosthesis 720 in a lumenof a patient during a medical procedure. These items are each describedin greater detail in PCT application WO98/53761. A self-expandingbranched prosthesis 750 similar to that described in reference to FIG.13b is also shown.

The bifurcated prosthesis 720 has a generally inverted Y-shapedconfiguration. The prosthesis 720 includes a body 723, a shorter leg 760and a longer leg 732. The bifurcated prosthesis 720 comprises a tubulargraft material, such as polyester, with self-expanding stents 719attached thereto. The self-expanding stents 719 cause the prosthesis 720to expand following its release from the introducer 700. The prosthesis720 also includes a self-expanding Z-stent 721 that extends from itsproximal end. The self-expanding Z-stent 721 has distally extendingbarbs 751. When it is released from the introducer 700, theself-expanding Z-stent 721 anchors the barbs 751, and thus the proximalend of the prosthesis 720, to the lumen of the patient. As analternative to the prosthesis 720 shown in FIG. 43, a prosthesis such asthat shown in FIG. 6 could be deployed followed by renal branchextensions; this would have the added benefit of excluding anyaneurysmal tissue in the renal arteries and allowing the aortic graft toextend further proximally. The self-expanding branched prosthesis 750 issimilar to the branched prosthesis described in reference to FIG. 13band is configured to form a tromboning connection with the shorter leg760 of the bifurcated prosthesis 720 and with a branch extension. Anotch or scallop may be cut into the proximal end of the branchedprosthesis 750 to facilitate deployment of the module.

The introducer 700 includes an external manipulation section 780, adistal attachment region 782 and a proximal attachment region 784. Thedistal attachment region 782 and the proximal attachment region 784secure the distal and proximal ends of the prosthesis 720, respectively.During the medical procedure to deploy the prosthesis 720, the distaland proximal attachment regions 782 and 784 will travel through thelumen to a desired deployment site. The external manipulation section780, which is acted upon by a user to manipulate the introducer, remainsoutside of the patient throughout the procedure.

The proximal attachment region 784 of the introducer 700 includes acylindrical sleeve 710. The cylindrical sleeve 710 has a long taperedflexible extension 711 extending from its proximal end. The flexibleextension 711 has an internal longitudinal aperture (not shown). Thislongitudinal aperture facilitates advancement of the tapered flexibleextension 711 along an insertion wire (not shown). The longitudinalaperture also provides a channel for the introduction of medicalreagents. For example, it may be desirable to supply a contrast agent toallow angiography to be performed during placement and deployment phasesof the medical procedure.

A thin walled metal tube 715 is fastened to the extension 711. The thinwalled metal tube 715 is flexible so that the introducer 700 can beadvanced along a relatively tortuous vessel, such as a femoral artery,and so that the distal attachment region 782 can be longitudinally androtationally manipulated. The thin walled metal tube 715 extends throughthe introducer 700 to the manipulation section 780, terminating at aconnection means 716.

The connection means 716 is adapted to accept a syringe to facilitatethe introduction of reagents into the thin walled metal tube 715. Thethin walled metal tube 715 is in fluid communication with the apertures712 of the flexible extension 711. Therefore, reagents introduced intoconnection means 716 will flow to and emanate from the apertures 712.

A plastic tube 741 is coaxial with and radially outside of the thinwalled metal tube 715. The plastic tube 741 is “thick walled”—its wallis preferably several times thicker than that of the thin walled metaltube 715. A sheath 730 is coaxial with and radially outside of theplastic tube 741. The thick walled plastic tube 741 and the sheath 730extend distally to the manipulation region 780.

During the placement phase of the medical procedure, the prosthesis 720is retained in a compressed condition by the sheath 730. The sheath 730extends distally to a gripping and hemostatic sealing means 735 of theexternal manipulation section 780. During assembly of the introducer700, the sheath 730 is advanced over the cylindrical sleeve 710 of theproximal attachment region 784 while the prosthesis 720 is held in acompressed state by an external force. A distal attachment (retention)section 740 is coupled to the thick walled plastic tube 741. The distalattachment section 740 retains a distal end 742 of the prosthesis 720during the procedure. Likewise, the cylindrical sleeve 710 retains theself-expanding Z-stent 721.

The distal end 742 of the prosthesis 720 is retained by the distalattachment section 740. The distal end 742 of the prosthesis 720 has aloop (not shown) through which a distal trigger wire (not shown)extends. The distal trigger wire extends through an aperture (not shown)in the distal attachment section 740 into an annular region between thethin walled tube 715 and the thick walled tube 741. The distal triggerwire extends through the annular space to the manipulation region 780.The distal trigger wire exits the annular space at a distal wire releasemechanism 725.

The external manipulation section 780 includes a hemostatic sealingmeans 735. The hemostatic sealing means 735 includes a hemostatic seal(not shown) and a side tube 729. The hemostatic sealing means 735 alsoincludes a clamping collar (not shown) that clamps the sheath 730 to thehemostatic seal, and a silicone seal ring (not shown) that forms ahemostatic seal around the thick walled plastic tube 741. The side tube729 facilitates the introduction of medical reagents between the thickwalled tube 741 and the sheath 730.

A proximal portion of the external manipulation section 780 includes arelease wire actuation section that has a body 736. The body 736 ismounted onto the thick walled plastic tube 741. The thin walled tube 715passes through the body 736. The distal wire release mechanism 725 andthe proximal wire release mechanism 724 are mounted for slidablemovement onto the body 736.

The positioning of the proximal and distal wire release mechanisms 724and 725 is such that the proximal wire release mechanism 724 must bemoved before the distal wire release mechanism 725 can be moved.Therefore, the distal end 742 of the prosthesis 720 cannot be releaseduntil the self-expanding Z-stent 721 has been released, and the barbs751 have been anchored to the lumen. Clamping screws 737 preventinadvertent early release of the prosthesis 720. A hemostatic seal (notshown) is included so that the release wires can extend out through thebody 736 without unnecessary blood loss during the medical procedure.

A distal portion of the external manipulation section 780 includes a pinvise 739. The pin vise 739 is mounted onto the distal end of the body736. The pin vise 739 has a screw cap 746. When screwed in, vise jaws(not shown) of the pin vise 739 clamp against or engage the thin walledmetal tube 715. When the vise jaws are engaged, the thin walled tube 715can only move with the body 736, and hence the thin walled tube 715 canonly move with the thick walled tube 741. With the screw cap 746tightened, the entire assembly can be moved together as one piece.

A second introducer may be used to introduce the helical branchedprosthesis 750 and create a tromboning connection. This secondintroducer may be based on the same principles as the introducer 700described above, but could be less complex. For example, the secondintroducer may include a sheath for containing the branched prosthesis750 in a compressed state, so that it can be introduced into a targetedanatomy and then released to either self-expand or be actively expandedwith a balloon. The second introducer could be equipped with a deliverytip 800, as shown in FIG. 44, to allow for the deployment of a guidewire 802 into the aortic bifurcation. A third introducer may be used todeploy the branch extension.

Deployment

Prosthetic modules are preferably deployed seriatim. The intermodularconnection between the branched prosthesis 750 and the bifurcatedprosthesis 720 is formed in situ. First the bifurcated prosthesis 720 isdeployed, and then the branched prosthesis 750 is deployed. For example,a bifurcated aortic prosthesis 720, as described in WO98/53761, can bedeployed into the abdominal aorta. The bifurcated prosthesis 720 has agenerally inverted Y-shaped configuration having a body portion 723, ashorter leg 760 and a longer leg 732. The body of the prosthesis isconstructed from tubular woven polyester fabric. At the proximal end ofthe prosthesis 720 is a self-expanding stent 721 which extends beyondthe end of the prosthesis and has distally extending barbs 751. Theshorter leg 760 and the longer leg 732 have internal projectionsextending from their distal termini.

This bifurcated prosthesis 720 can be deployed in any method known inthe art, preferably the method described in WO98/53761 in which thedevice is inserted by an introducer via a surgical cut-down into afemoral artery, and then advanced into the desired position over a stiffwire guide using endoluminal interventional techniques. For example, aguide wire (not shown) is first introduced into a femoral artery of thepatient and advanced until its tip is beyond the desired deploymentregion of the prosthesis 720. At this stage, the introducer assembly 700is fully assembled, and ready for introduction into the patient. Theprosthesis 720 is retained at one end by the cylindrical sleeve 710 andthe other by the distal attachment sections 740, and compressed by thesheath 730. If an aortic aneurism is to be repaired, the introducerassembly 700 can be inserted through a femoral artery over the guidewire, and positioned by radiographic techniques, which are not discussedhere.

Once the introducer assembly 700 is in the desired deployment position,the sheath 730 is withdrawn to just proximal of the distal attachmentsection 740. This action releases the middle portion of the prosthesis720 so that it can expand radially. The proximal self-expanding stent721, however, is still retained within the cylindrical sleeve 710. Also,the distal end 742 of the prosthesis 720 is still retained within theexternal sheath 730.

Next, the pin vise 739 is released to allow small movements of the thinwalled tube 715 with respect to the thick walled tube 741. Thesemovements allow the prosthesis 720 to be lengthened or shortened orrotated or compressed for accurate placement in the desired locationwithin the lumen. Radiopaque markers (not shown) may be placed along theprosthesis 720 to assist with placement of the prosthesis.

When the proximal end of the prosthesis 720 is in place, the proximaltrigger wire is withdrawn by distal movement of the proximal wirerelease mechanism 724. The proximal wire release mechanism 724 and theproximal trigger wire can be completely removed by passing the proximalwire release mechanism 724 over the pin vise 739, the screw cap 746, andthe connection means 716.

Next, the screw cap 746 of the pin vise 739 is then loosened. After thisloosening, the thin walled tube 715 can be pushed in a proximaldirection to move the cylindrical sleeve 710 in a proximal direction.When the cylindrical sleeve 710 no longer surrounds the self-expandingstent 721, the self-expanding stent 721 expands. When the self-expandingstent 721 expands, the barbs 751 grip the walls of the lumen to hold theproximal end of the prosthesis 720 in place. From this stage on, theproximal end of the prosthesis 720 cannot be moved again.

Once the proximal end of the prosthesis 720 is anchored, the externalsheath 730 is withdrawn to distal of the distal attachment section 740.This withdrawal allows the contralateral limb 760 and the longer leg 732of the prosthesis 720 to expand. At this point, the distal end 742 ofthe prosthesis 720 may still be moved. Consequently, the prosthesis 720can still be rotated or lengthened or shortened for accuratepositioning. Such positioning of the prosthesis 720 may ensure that theshorter leg 760 extends in the direction of a contralateral artery.

After the shorter leg 760 extends in the direction of the contra-iliacartery, the branched prosthesis 750 is deployed. The branched prosthesis750 is deployed such that it forms a tromboning connection with theshorter leg 760 and extends from the shorter leg 760 into thecontralateral artery. The coupling of the prosthesis 720 and branchedprosthesis 750 is described in greater detail in other portions of thisdisclosure.

The method of introduction of the branched prosthetic module 750 may beas follows. A guide wire (not shown) is introduced into thecontralateral femoral artery and advanced until its tip is above theregion into which the prosthesis is to be deployed. The secondintroducer is then advanced over the guide wire with an oscillating androtating action until the extension prosthesis is overlapped one fullstent within the contralateral limb 760. A final position check may thenbe made before the sheath is withdrawn while holding the thick walledtube in place. A similar methodology for deployment of a hypogastricbranch graft module is described and illustrated in a U.S. PatentApplication Publication No. 2005/0182476, which is incorporated hereinby reference.

The guide wire 602 can be deployed from the tip 600 of the secondintroducer captured and pulled over to the ipsilateral side tofacilitate deployment of a third introducer through the ipsilateral sideinto the contralateral side to deploy a branch extension into thehypogastric artery. Preferably, a preloaded wire or snare within thelimb of the prosthetic branch will preclude the need for complexlocalization, catheterization of branches and separate insertion of thewire through the sheath. This approach may be particularly importantwhen multiple branches are present. The distal handle of the deliverysystem may be equipped with an additional trigger wire to accommodatethis feature. The second and third introducers and the methods of usingthem are described in greater detail in U.S. patent application,“Introducer for an Iliac Side Branch Device,” Ser. No. 60/510,823, filedOct. 14, 2003, which is incorporated herein by reference.

The introducer and deployment method described above can be adapted forimplantation in other regions. For example, if a first prosthetic moduleis placed into the aorta, a connecting prosthetic module can be placedinto the renal, iliac, superior mesenteric, celiac or other artery toform a tromboning interconnection. If a first prosthetic module isplaced into the thoracic aorta, a connecting prosthetic module can beplaced into another portion of the thoracic aorta, the left subclavian,left common carotid, innominate or other artery. Furthermore, prostheticmodules which are implanted in the same artery can be connected to eachother. The overlap region of each of these embodiments is preferablyadapted to the size of the relevant anatomy and the forces to which theprostheses are exposed in the relevant anatomy.

Example 1

The flow force on the branched limb is dependent upon the loads appliedto the branch point and ultimate angulation of the prosthetic branch. Ofparticular interest are the forces that may cause separation of thebranch extension from the prosthetic branch. Forces due to flow in they-direction, if significant enough, can become larger than thefrictional forces that hold the branch extension and the prostheticbranch together, resulting in separation. If the separation issubstantial, a type III endoleak will occur and the aneurysm will nolonger be excluded.

The prostheses described above may be subjected to an in vitro leakpressure test. The purpose of this test procedure is to determine theminimum internal pressure required causing leakage at the mating pointbetween two prostheses.

The test requires a pressure transducer, a pressure monitor,water/glycerin mixture (dyed) @ 3.64 cP, water bath, submersible heater,water pump, temperature controller, mating surface thermocouple, andmercury thermometer.

The prosthetic branch and branch extension are mated such that there isa suitable tromboning connection, preferably with a 1.5-2 cm overlap anda 1 mm or less difference in diameter at the interconnection. Thedevices may be ballooned for 30 seconds using a suitably sized balloondilation catheter.

Internal pressure in the mated devices is measured utilizing a pressuretransducer and pressure monitor. These instruments are connected to asyringe providing manually controlled pressure into the mated devices.The pressure liquid is a glycerin/water mixture to 3.64 centiPoise (cP)dyed with blue food coloring. The device was placed in a 37° C. waterbath and the presence of a leak would be defined and identified byleakage of the blue-dyed glycerin/water mixture. Visual accounts ofleakage and a recording of peak pressures were manually recorded.

Example 2

The prostheses described above may be subjected to an in vivo test,preferably in non-human mammals. One animal that is suitable forimplantation of the prosthesis for testing and therapeutic purposes isthe domestic cow. For testing purposes, six- to ten-week-old male calveswere used.

As presurgical preparation, each animal was given a daily dose of 325 mgof aspirin beginning on the day prior to the procedure for the purposeof platelet inhibition. Each animal was kept without food forapproximately 8-12 hours and without water for approximately 2 hourspreceding each procedure. A pre-operative baseline ACT was measured in aHemochron Jr. Signature Series Machine® (available from ITC in Edison,N.J.).

Each calf was sedated with Xylazine (1.0 mg/10 lbs, IM). Once the animalwas lightly sedated, an induction mask was used to deliver Isofluorane(2-4%). The calf's face was placed into the mask while the inhalationanaesthetic was delivered. The animal may be intubated in standardfashion. Once the endotracheal tube was placed, it was secured. Theventilator was turned on and connected to the animal to increase thedepth of anesthesia and mechanically ventilate the animals. Isofluoranedosages ranged from approximately 0.8-1.25%, although may be anypercentage based on relevant factors. During this pre-surgicalpreparation, each animal may also receive an injection of benzathineprocaine penicillin (30,000-50,000 U/kg IM).

The animal was placed on its left side with its right hind leg extendedup and secured with gauze ties. A ground pad and EKG leads were placedon the animal. An intravenous catheter (IV) was placed in the peripheralleg vein and secured with tape. Lactate Ringers (LR) was infused throughthe catheter for the duration of the procedure to provide adequatehydration. Both groins were shaved and sterilely prepped with 70%alcohol and betadine.

The implantation of this branched vessel device involved basicendovascular techniques. A femoral cutdown was performed on the left legto gain access to a femoral vessel. A retroperitoneal incision wasperformed to provide access to the right iliac artery. A third accesspoint was gained via a cutdown exposing the right carotid artery.Hemostatic vessel loops were placed proximally and distally on thearteries. A single wall puncture needle was used to access the leftfemoral artery, and conformation of the cannulation was confirmed by thepresence of pulsatile arterial flow from the needle hub.

Once the pulsatile flow was observed, a wire was placed in thedescending abdominal aorta. The animal was heparinized with 200 IU ofporcine heparin/kg. An activated clotting time was obtained within 3-10minutes following heparin administration to ensure adequateanti-coagulation, to achieve a preferred minimum of 1.5-2 times thebaseline ACT. An 8 French introducer sheath was advanced into the leftarterial lumen. Before and after placement, the side port of each sheathwas flushed with 0.9% normal saline.

A 5 French pigtail catheter was inserted over the wire through theintroducer sheath and advanced into to the region of the aortic archusing fluoroscopic guidance. A baseline digital subtraction angiogram ofthe descending thoracic aorta was obtained utilizing an appropriate doseof contrast. Once the baseline angiogram had been achieved, a wire wasplaced through the pigtail catheter and advanced into the thoracicaorta. The catheter was then removed. A 12.5 MHz Boston Scientific IVUS(intravenous ultrasound) probe was inserted over the wire in a monorailfashion, and baseline IVUS measurements were obtained. Thesemeasurements included cross-sectional diameters of the distal abdominalaorta approximately 9 cm proximal to the trifurcation.

An external helical device similar to that shown in and described inreference to FIG. 11 was employed. This particular prosthesis wasmanufactured from a Viabahn® Endoprosthesis (W. L. Gore & Associates,Inc., Newark, Del.), which is made from expanded PTFE. It was loadedinto an 18 French cartridge with a 4 French catheter providing 0.035inch wire access through the man device and a preloaded 0.018 inch wirewithin the branched limb.

A single wall puncture needle was used to access the right iliac artery.Once an Amplatz guide wire was placed, a 20 French Check-Flo® (CookIncorporated, Bloomington, Ind.) introducer sheath was advanced to 9 cmabove the aortic bifurcation and utilized as the delivery system. Thepreloaded 0.018 inch wire was advanced through the valve of theCheck-Flo® sheath using a peal-away sheath. The loaded device cartridgewas then inserted into the 20 French Check-Flo® using the dilators aspushers. The 0.018 inch wire was snared from the carotid artery toprovide through-and-through access for the branch vessel wire. Theprosthesis was then deployed to the point that the ostium of theprosthetic branch was exposed. The prosthesis was then advanced throughthe contralateral femoral artery.

The prosthesis was deployed with a 2.0 cm overlap within the prostheticbranch. The entire length of the prosthesis was ballooned with a 7 mm×4cm balloon. Post implant angiographic and IVUS assessments wereperformed. The final IVUS assessment measured the proximal, mid anddistal points of the stent graft along with the ostium, while theangiogram assessed the presence of any endoleaks, as well as thelocation of the stent graft. If desirable, the prosthesis may beexplanted and subjected to post-explant analysis.

Example 3

One helical branch vessel stent graft is deployed such that the branchis properly oriented with respect to the internal iliac artery. Fourmarkers on the distal end of the branch are placed approximately 5 mmabove the internal iliac artery. The sheath housing the device iswithdrawn to expose the branch limb, leaving the distal end constrainedwithin the sheath in the external iliac artery. The wire dwelling withinthe contralateral limb is replaced with a steerable guidewire, which isthen advanced into the distal aorta and snared with a snare deviceintroduced from the contralateral femoral artery. This provides accessfrom the contralateral groin, through the proximal aspect of the iliacbranch, into the iliac limb, and then alongside the outer portion of thedistal segment (external iliac artery segment) to the ipsilateral groin.

Over this through-and-through wire, a 10F or 12F Balkin sheath (CookIncorporated, Bloomington, Ind.) is introduced and advanced into theside branch limb. Alongside the through-and-through guidewire, asteerable catheter and wire combination is advanced and utilized toselectively cannulate the internal iliac artery.

Once a reasonable purchase is established, a stiffer wire is placed andthe mating component is advanced into the desired position. The matingcomponent may be a Viabahn® graft which is advanced into the hypogastricartery so that it has preferably a 2 cm minimum overlap with the helicalbranch. Once the mating graft is deployed and appropriately ballooned,the remainder of the external iliac limb is deployed. The component isthen mated to the remainder of the Zenith® graft with the modified 12 mmextension described in FIG. 3 c.

Although the invention has been described and illustrated with referenceto specific illustrative embodiments thereof, it is not intended thatthe invention be limited to those illustrative embodiments. Thoseskilled in the art will recognize that variations and modifications canbe made without departing from the true scope and spirit of theinvention as defined by the claims that follow. It is therefore intendedto include within the invention all such variations and modifications asfall within the scope of the appended claims and equivalents thereof.

The invention claimed is:
 1. A branched prosthesis comprising: a tubular body of biocompatible graft material having, a first end, a first portion, a second end, a second portion, a lumen between the first and second ends, a sidewall between the first and second ends, a first fenestration in the side wall in the first portion and having an internal branch attached to the side wall at the fenestration and extending from the fenestration into the lumen, the internal branch having a first end communicating with the fenestration and a second end having an opening extending toward the first end; at least one second fenestration in the sidewall spaced axially from the first fenestration and having an external branch attached to the side wall at the fenestration and extending from the side wall with a first end communicating with the fenestration and a second end extending toward the second end; and a plurality of stents attached along the length of the tubular body.
 2. The branched prosthesis of claim 1, wherein the first end is the proximal end and the second end is the distal end.
 3. The branched prosthesis of claim 1, further having a bare stent extending from one of the first and second ends.
 4. The branched prosthesis of claim 1, wherein the internal branch extends at least partially helically along an internal surface of the tubular body.
 5. The branched prosthesis of claim 1, wherein at least one of the branches is stented.
 6. The branched prosthesis of claim 5, wherein all of the branches are stented.
 7. The branched prosthesis of claim 1, wherein the first portion has a first diameter and the second portion has a second diameter less than the first diameter and the first fenestration is in the sidewall of the first portion.
 8. A branched prosthesis comprising: a tubular body of biocompatible graft material having, a proximal end, a proximal portion, a distal end, a distal portion, a lumen between the proximal and distal ends, a sidewall between the proximal and distal ends, a first fenestration in the side wall in the proximal portion and having an internal branch attached to the side wall at the fenestration and extending from the fenestration into the lumen, the internal branch having a first end communicating with the fenestration and a second end having an opening extending toward the proximal end; at least one second fenestration in the sidewall distal of the first fenestration and having an external branch attached to the sidewall at the fenestration and extending from the side wall with a first end communicating with the fenestration and a second end extending toward the distal end; and a plurality of stents attached along the length of the tubular body.
 9. The branched prosthesis of claim 8, wherein the proximal portion has a first diameter, the distal portion has a second diameter less than the first diameter, and the first fenestration is in the sidewall in the proximal portion.
 10. The branched prosthesis of claim 8, further having a bare stent extending from the proximal end of the tubular body.
 11. The branched prosthesis of claim 8, wherein the internal branch extends at least partially helically along an internal surface of the tubular body.
 12. The branched prosthesis of claim 8, wherein at least one of the branches is stented.
 13. The branched prosthesis of claim 8, wherein all of the branches are stented.
 14. A branched stent graft comprising: a tubular body of biocompatible graft material having, a proximal end, a distal end, a lumen between the proximal and distal ends, a sidewall between the proximal and distal ends, at least two branches attached to the sidewall and extending from the side wall, each having an end opening pointing toward the proximal end of the tubular body; at least one branch attached to the sidewall and extending from the sidewall and having an end opening pointing toward the distal end of the tubular body, wherein at least one of the proximally pointing branches is an internal branch, and wherein the tubular body and the branches each comprise at least one stent.
 15. The branched stent graft of claim 14, wherein the proximally pointing branches are axially spaced from the at least one distally pointing branch.
 16. The branched stent graft of claim 14, where the proximally pointing branches are circumferentially spaced from each other.
 17. The branched stent graft of claim 14, further comprising two distally pointing branches. 